Exploring an Extended Reality Floatation Tank Experience toReduce the Fear of Being in Water
Maria F. Montoya

Hannah Qiao

Prasanth Sasikumar

maria@exertiongameslab.org
Monash University
Melbourne, Australia

hannah@ahlab.org
National University of Singapore
Singapore, Singapore

prasanth.sasikumar@nus.edu.sg
National University of Singapore
Singapore, Singapore

Don Samitha Elvitigala

Sarah Jane Pell

Suranga Nanayakkara

don.elvitigala@monash.edu
Monash University
Melbourne, Australia

research@sarahjanepell.com
Monash University
Melbourne, Australia

suranga@ahlab.org
National University of Singapore
Singapore, Singapore

Florian ‘Floyd’ Mueller
floyd@exertiongameslab.org
Monash University
Melbourne, Australia

Figure 1: Participant floating in a floatation tank using the extended reality system used in this study

ABSTRACT
People with a fear of being in water rarely engage in water activities
and hence miss out on the associated health benefits. Prior researchsuggested virtual exposure to treat fears. However, when it comesto a fear of being in water, virtual water might not capture water’s
immersive qualities, while real water can pose safety risks. We propose extended reality to combine both advantages: We conducteda study (N=12) where participants with a fear of being in waterinteracted with playful water-inspired virtual reality worlds while
floating inside a floatation tank. Our findings, supported quantitatively by heart rate variability and qualitatively by interviews,
suggest that playful extended reality could mitigate fear responses
in an entertaining way. We also present insights for the design offuture systems that aim to help people with a fear of being in waterand other phobias by using the best of the virtual and physicalworlds.

KEYWORDS
water, fear of being in water, extended reality, floatation tank, flotation pod, exposure therapy, phobia, virtual reality
ACM Reference Format:
Maria F. Montoya, Hannah Qiao, Prasanth Sasikumar, Don Samitha Elvitigala, Sarah Jane Pell, Suranga Nanayakkara, and Florian ‘Floyd’ Mueller.
2024. Exploring an Extended Reality Floatation Tank Experience to Reduce
the Fear of Being in Water. In Proceedings of the CHI Conference on Human
Factors in Computing Systems (CHI ’24), May 11–16, 2024, Honolulu, HI, USA.
ACM, New York, NY, USA, 17 pages. https://doi.org/10.1145/3613904.3642285

1

INTRODUCTION

Being in water has many mental, physical, and cultural benefits[24, 47, 88, 112]. However, people without access to bodies of water,such as public swimming pools and oceans, rarely experience water
activities. This lack of access, and other cultural and skill-based
reasons [80, 82, 105], offer possible explanations for a fear of being
in water, or Aquaphobia [82]. Fear of being in water is an aversion
to being in the water, and Aquaphobia is the clinically diagnosed
irrational fear of water (i.e., a persistent fear with an inability toovercome it) [74, 80, 91]. People who fear being in water are often
unable to enjoy recreational and playful activities in water, such asat swimming pools or beaches [80] and can even develop a fear ofdrowning [1, 13]. We believe there is an opportunity for interactive
systems to bring people closer to water in fun and accessible ways.
Although Human-Computer Interaction (HCI) researchers havedeveloped tools for phobia treatment aiming to help people withspecific fears [17], and the WaterHCI area (focused on the creationof interactive systems tailored for water-related activities [25, 73,84]) keeps gaining attention, little knowledge exists on the use ofPermission to make digital or hard copies of all or part of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for components of this work owned by others than theauthor(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or
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ACM ISBN 979-8-4007-0330-0/24/05
https://doi.org/10.1145/3613904.3642285

interactive systems to reduce the fear of being in water [101, 106,116]. With such knowledge, we believe we could begin reducing
the barriers to accessing aquatic activities’ physical and mental
benefits.
In prior work, we presented an extended reality (XR) systemthat offers a playful water experience in a floatation tank, bringing
people closer to water as well as allowing relaxation and entertainment [84, 85]. We are interested in the potential of this XR system
to reduce people’s fear of being in water. We hypothesized that thisXR system could mitigate the fear of being in water for three main
reasons. Firstly, floatation tanks are a controlled water environment (compared to dynamic natural water environments) and theirsalt-water buoyancy affords effortless floating, so people need little
effort to stay afloat and can more easily enjoy their bodies being inwater, similar to people who receive help to learn to float in pools[60, 110]. Secondly, the system’s VR component (comprising different VR environments with hear rate biofeedback, thereby providing
an extended immersive water environment) guides participants torelax and explore water worlds (real and virtual), similar to virtual
reality exposure therapy (VRET), which progressively engages people to a fearful situation [17, 99, 108]. Thirdly, the system rewards
participants with a playful experience through an entertaining interactive story, that could engage participants to be in water, similar
to games used for VRET to engage people with the fearful element[8, 39, 79],
As an initial exploration of sensitizing people to water in general, we examined the XR system’s feasibility to help a sub-clinicalpopulation of people with fear of being in water (Fig. 1). We conducted a mixed-method controlled study to investigate the researchquestion: How does an XR system within a floatation tank influence people’s perceived fear of being in water? Using heart ratevariability (HRV) analysis, statistical analysis of anxiety and fearof water questionnaires, and thematic analysis of semi-structured
interviews, we analyzed participants’ perceived fear of being inwater and their user experiences (UX). Our paper’s contributionsare:• The articulation of participants’ subjective UX with the XR
system and their willingness to use interactive technology inwater, which might be useful to WaterHCI researchers anddesigners interested in developing interactive technology
not just for people with fears, but possibly for general healthand wellbeing.
• The analysis of participants’ HRV data, providing insights
into the influence of combining water and interactive technology, which could be useful for WaterHCI designers interested in reducing the fear of being in water.
• Four design strategies to inspire stakeholders, such as psychologist, health practitioners, and wellbeing designers interested in wellbeing applications to use interactive technology
as a tool in the treatment of fear of being in the water andpossible for other phobias.
If XR systems like the one investigated in this study can help
people reduce their fear of being in water, we believe that people
would be more likely to engage in playful water activities and hence
profit from the associated benefits. Moreover, we see our work not

A XR floatation tank experience to reduce the fear of being in water

as a conclusion on the topic, but rather as a stepping stone towards
more work on the use of XR and water to help people.

2 RELATED WORK
2.1 Fear of being in water and Aquaphobia
Fear of water is characterized by a feeling of aversion towards
water, and can be overcome [74]. Aquaphobia, an extreme fearof water, is clinically diagnosed as irrational and persistent, andcannot be overcome [74, 80, 91]. Psychology researchers [6, 78, 80]
categorize the fear of being in water as a "specific phobia". Cognitive
researchers have also investigated associated fears of being in water[70]. Although we are not investigating clinically diagnosed fear of
being in water, we learned from this prior work that many factors
influence fear of being in water, including past bad experiences andlack of skills to floating or moving in water, leading to a fear ofdrowning [13, 82, 97]. Consequently, we took these reasons into
account when proposing different technologies as tools to reduce
people’s fear of being in water.
We have also learned from sports scientists that fear of being
in water can be a barrier to performing water activities such as
swimming, and sports researchers have investigated playful ways
to reduce this fear, such as through water play activities [13, 62,
81, 90, 111]. While this research shows us that progressive, playful
water contact can help people feel more comfortable in water, ourwork aims to contribute knowledge about how fear of being inwater could be mitigated in the future through a combination ofwater and interactive technology.

2.2

Floatation tanks as psychological therapy

Psychologists originally designed floatation tanks, also known as
sensory deprivation tanks, to conduct psychological studies or "restricted environmental stimulation therapy" (REST) [66, 67, 118,120]. Floatation tanks enabled a specific type of REST, called “floatation therapy” [67, 120], that researchers demonstrated could be
useful for patients with health disorders including hypertension[118], chronic pain [67], anxiety [35], burnout syndrome, and stress[59, 120]. While floatation therapy has been shown to reduce anxiety, which is the main symptom in fear response [80, 99], and many
floatation centers advertise this benefit [57], there is little researchon its use for specific phobias [58]. To the best of our knowledge,
there are no investigations into the use of technology in floatation
sessions to reduce fear of being in water. Nevertheless, floatation inpools is a common step towards overcoming fear of being in water
when learning to swim [81, 82, 90, 110], which indicates its efficacy
in reducing fear of being in water.

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

touch could trigger a response in people who have a fear of being inwater. On the one hand, as exposure therapy has suggested, exposing people to water may increase their anxiety [17]. On the other
hand, as a controlled water environment in which people can float
effortlessly, the floatation tank may reduce participants’ anxiety.
Hoffman et al.’s [50, 51] research results could be an indicator of thissecond possibility, given that they achieved pain reductions whencombining wound treatment in a hydrotank with a water-related
VR visualization.
Researchers have proposed VR environments to address fear instressful situations [96] and treat phobias [17], such as arachnophobia (fear of spiders) [33, 41] and claustrophobia (fear of being inclosed spaces) [20] under the term "virtual reality exposure therapy"(VRET) [17, 99]. VRET reduces anxiety, the basic phobia response[17, 99, 128]. Recent work investigated the use of VRET for waterrelated phobias, such as squalophobia (fear of sharks) [70] and thalassophobia (fear of large bodies of water) [95]. While these works
showed us that virtual undersea environments tend to induce fear
responses and that progressive exposure to VR water environments
offers a first step toward overcoming water-related fear, there arefew systematic VRET investigations into fear of being in water.
We consider VRET to have great potential given that WaterHCI
research has used VR headsets in pools [3, 100] and floatation tanks
for physical rehabilitation and recreational purposes [4, 84, 85].
However, there exists little insight into people’s UXs of being in
the water while using this technology [84] or, more specifically,
whether people with a fear of being in water are willing to use thistechnology, and the impact it may have on their fears or perceptions
towards water.
Furthermore, very few investigations have proposed VR as partof a treatment for fear of being in water. In one example, Rocheet al. [101] proposed 360° videos of aquatic environments to help
children relax and climatize to water before a swimming lesson.
We note that their research participants (2 swimming students, 11
and 12 years old) did not have contact with physical water during
the 360° video projection; in contrast, our study participants did.
Although Yang et al [106] developed a system for VR use in apool for fear of water, they did not evaluate it with people withfear of water; hence, we extend this prior work with a systematic
evaluation. While Adhatrao et al. [5] speculated on the use of a VR
environment and physiological sensors for treating fear of being inwater, they did not develop the systems or undertake a user study.
While there has been some exploration of VRET use to treat fear of
being in water, there is little evidence of its use and evaluation in awater environment.

2.4
2.3

Virtual reality as therapy for phobias andfear of being in water

HCI researchers have proposed virtual water environments to treat
anxiety, suggesting that water-related visualizations and soundscapes could induce relaxation [9, 56, 121]. Interestingly, Hafsteisson et al. [45] proposed a virtual visualization of water to potentiallyinduce fear of water, without utilizing the physical water’s tactile
stimuli that could also induce fear of water. We believe that the
combination of water-related virtual elements and water’s physical

Virtual reality exposure therapy (VRET)
evaluation

Given our interest in the UXs, we also learned from prior studies
evaluating VRET efficacy and UXs. For example, researchers studied
healthy volunteers in a VR environment as a treatment tool forclaustrophobia [20], evaluating it using claustrophobia and anxiety
questionnaires. Since these questionnaires proved useful, and havebeen used in clinical trials of phobias [6, 35, 83, 108, 125], we also
use them in our work and complement them with qualitative datafrom interviews to enrich our understanding of the UX and derive

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

insights for future designs. Furthermore, VRET researchers haveused biosignals to measure fear responses during VRET for fear offire, reporting encouraging results [117, 128]. While these works
used biosignals in on-land settings, we were inspired to use biosignals in our work because they provide a quantitative measurementof fear [23], the proposed XR system already incorporates heart
rate biofeedback [84], and prior work has indicated the feasibilityof biosignal measurements in floatation tanks [102].
Therefore, we looked at heart rate variability (HRV), a measurement that has previously been used to understand anxiety responses
associated with fear [12, 16, 23, 27, 42, 117]. HRV refers to the variation between heartbeat intervals and reflects the autonomic nervous
system’s (ANS) influence on the heart. The ANS is known to regulate the fear responses and can be analyzed using HRV [12, 23]. We
believe that interactions with this XR system could decrease theanxiety response of participants who have a fear of being in water.
To begin understanding this effect, we investigated the differencesin HRV measurements of participants floating with the XR system
and without it. We hypothesized that a significant decrease in HRV
indexes reflecting participants’ anxiety levels could be found while
participants use the XR system.

3

EXTENDED REALITY SYSTEM

We used an XR system as a research vehicle. This system offers anovel experience within a floatation tank [84], categorized as an
XR experience according to Milgram’s reality-virtuality continuum[71, 93]. The experience involves floating in the tank while a VR
headset (Meta Quest 2) delivers a virtual auditory and visual environment. The participant’s HR (sensed using the polar verity sensor[2]), breathing (sensed via the headset’s microphone), and slighthead movements (sensed via the headset’s IMU sensors) control
interactions within the virtual environment.
This XR experience provides an interactive journey where theparticipant is guided through three main virtual water worlds (Fig.
2C, Fig. 2D, Fig. 2E ) by a virtual character called “water spirit"(which looks like a cinematic mystical water figure (Fig. 2A)). The
water spirit is a guide that provides the participant with verbal
assurances that they are doing fine and are safe and encourages
them to enjoy the experience. We developed this experience in priorwork [84], where through a somaesthetic approach, we provide thedesign decisions to create a playful floatation tank experience. In
addition to the reasons pointed out in the introduction section arguing why we hypothesized that this XR system could mitigate thefear of being in water, we resonate with the following decisions wemade when designing this system even though it was not originallydesigned for fear [84]:• We believe that the "journey" in this VR experience could
be seen as similar to the exposure therapy’s "step-by-step"
progressive exposure of participants to a fearful situation[17, 124]. For example, the VR journey starts with the water
spirit guiding and accompanying the participant to be in contact with water entering a calm ocean (Fig. 2B). Then, they
progress to sink into an underwater world (Fig. 2C), in which
the participant is encouraged to control their breath anddiscover the environment. Second, the participant’s avatar(guided by the water spirit) moves to a calmer space-likeMontoya et al.

world without virtual contact with water (Fig. 2D), in which
the participant is invited to collaborate with the water spirit
to collect virtual water balls.
• We found the final stage of the VR journey is analogous tothe challenging situations in water environments that sometimes can occur where it is vital to stay calm in order to
respond accordingly, for example, when getting into a ripin the ocean. In this final stage, the participant moves skyward (Fig. 2E), and the water spirit guides them to navigate
through cyclones and encourages them to control their heart
rate to stop the rain and storms (Fig. 2F).
• We created this hands-free interaction by using the headset’s IMU sensors and microphone, encouraging slow water
movements and facilitating body relaxation in water [84].
We found these interactions suitable for people with a fear of
being in the water since they would not have to be worried
about doing strenuous movements in their fearful environment.

4 USER STUDY
4.1 ParticipantsParticipants were recruited using advertisements sent to our mailing lists. Participants needed to have a self-described fear of being
in water, aged 18 years or older, be healthy, and confirm that they
suffered from none of a range of identified risk conditions or disabilities (consistent with previous work [67, 84]).
Twelve participants volunteered for the study (seven females
and five males) with a mean age of 30 years (standard deviationof ±2.82 years). No participant reported previous experience using
floatation tanks. Regarding their experience with VR technology,
six participants described themselves as novices (VR use once in a
lifetime or once per year), two as "average" (once a month), and four
reported no previous experience. In terms of their experience withaquatic environments, eight participants described themselves as
having "novice" experience in pools (mostly used once per year), andfour described themselves with "average" experience (mostly used
once per month). Only one participant self-described as having
novice experience in the ocean, and one had novice experience
visiting a water park. Five participants described themselves with aslight (f=1) fear of being in the water, five with a medium fear (f=2),
and two with a high (f=3) fear (on a scale from 0 = none to 4 = veryhigh). Ten participants completed the entire study procedure, while
two completed all but the last floatation part of the study.
We ensured that all personnel involved followed the local safety
guidelines for floatation practice as well as water and VR safety
best practice. The ethics committee of our institution approved
this study. No safety incidents occurred during the study, and theparticipants did not report any issues.

4.2

Measurements

The fear of water assessment questionnaire (FWAQ) [82] has helped
swimming teachers identify students with a fear of being in waterin order to change their coaching strategies. Misimi et al. [82]validated this questionnaire with 2,074 participants. We used thisquestionnaire as a screening tool to corroborate a participant’s
self-reported fear of being in water.

A XR floatation tank experience to reduce the fear of being in water

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

Figure 2: XR system’s virtual elements and VR worlds: A) the water spirit; B) introductory calm ocean; C) underwater world; D)space psychedelic world; E) sky world; and F) sky world when raining.
We created a site-specific assessment tool, the Ad-hoc aquatic
anxiety questionnaire (AAAQ), to gather participants’ subjective
anxiety levels. The assessment design needed to be short enoughto be administrated during the procedure breaks (see below). This
assessment consisted of five statements scored on a Likert scale(from one to five: 1= strongly disagree, 2 = disagree, 3 = not sure, 4= agree, 5 = strongly agree) with specific statements about feelings
that could be related to anxiety levels while in the water. The
statements included: "I feel calm", "I feel secure", "I feel comfortable","I am relaxed", "I feel nervous about water", and "I am worried aboutwater". These statements were extracted from the FWAQ [82] andthe anxiety STAI questionnaire [61, 109], which is a well-known
anxiety questionnaire often used in studies related to fear [40, 64]
and VRET [7, 8, 20, 70].
We conducted semi-structured interviews to assess the participant’s UXs. We used a semi-structured approach to leave sufficientroom to support deeper elucidation of participants’ responses. Finally, we recorded the photoplethysmography (PPG) [103] signal
using a second HR light sensor [2]. Participants’ PPG signal data,measured during the procedure, was stored in a .CSV file for later
analysis.

4.3

Procedure

The study was conducted in a commercial floatation center thatowns floatation tanks of 225mm long, 145mm wide, and 30mm ofwater depth. The tanks are located in private rooms with showers.
The lights remained on during the procedure, and the water temperature was 35°C. Our procedure had six stages (Fig. 3). In stage
one, we introduced participants to the procedure. The participants
completed the FWAQ. Then, we showed participants the floatation
room. Participants privately showered and changed into bathing
attire, then informed us of when they were ready by knocking
at the door. In stage two, we helped participants to put two HR
sensors on their arms, (one for the VR’s feedback loop and one for

the PPG recording) and asked them to lie still on a yoga mat for
5 minutes, while we recorded a baseline HR measurement. They
then completed the AAAQ.
Stage three comprised a floating period without technology. We
helped participants enter the floatation tank and provided guidanceon how to float. Once participants acknowledged that they were
floating and stable, we began the HR recording and asked them tofloat for 15 minutes. Next, they completed the AAAQ.
Stage four comprised a floating period using the XR systemdelivering the VR experience. We asked participants to stand up
inside the floatation tank and dry their hands. We then helped themto put on the VR headset and the VR experience lasted 15 minutes.
After this, we helped participants to remove their headset and they
completed the AAAQ.
In stage five, participants were asked to float without technology
again for 15 minutes with the HR still being recorded. They thencompleted the AAAQ again and exited the tank. We designed thesestages to last 15 minutes each, with a total time of 45 minutes
floating, aiming to offer a floating time similar to the commercial
floatation sessions (usually 45 minutes to 1 hour) and avoid the"mammal reflex"[11, 37]. Finally, in stage six, we left participantsalone in the room to take a shower and prepare for their interview.
The lid of the tank remained open during the floating stages since
we believed an enclosed space would enhance feelings of fear. For
safety reasons, the researchers also remained in the room (at adistance) and monitored the participants at all times.

4.4

Data analysis

The questionnaires were mean scored in a way that was consistent
with the scoring approach in prior work [82]. Additionally, the selfreported anxiety data was analyzed on a Likert scale. A repetitive
measure ANOVA was performed, to identify differences in the
anxiety level between the floating conditions. Additionally, weCHI ’24, May 11–16, 2024, Honolulu, HI, USA

Montoya et al.

Figure 3: The six stages in our procedure. Stage 1: introduction, screening questionnaire and participant’s preparation. Stage 2:
baseline. Stage 3: first floating (without the system). Stage 4: floating with the XR system delivering the VR experience. Stage 5:
second floating (without the system). Stage 6: participants showering and interview.
conducted a Holm post-hoc test when significant differences were
found.
To identify key themes, the semi-structured interviews wereanalyzed in NVivo using an inductive thematic analysis approach[18] and an open coding process. Each data unit was a single coded
quote, a practice we borrowed from others [10, 84, 104]. The coding
process was “data driven” to minimize bias, whereby two coders
worked separately and systematically through the entire data set(the interview notes transcripts), giving equal attention to eachdata item [18]. In total, the coders coded 420 units of data, whichwere subsequently grouped into high-level codes and discussed togenerate themes.
Participants’ PPG signal data were divided into the procedure
stages and pre-processed in 5-minute windows using a 3rd order Butterford bandpass filter with cut-off frequencies between
0.2hz and 2.5hz to eliminate trends, motion artefacts, and ambient
light noise. Peak-to-peak detection and the Heartpy python librarywere used to extract HRV from the pre-processed PPG signal. We
extracted time and frequency indexes from the HRV signal. We
focused our analysis on short-term indices such as the standard
deviation of NN intervals (SDNN) and the high-frequency of the HR
spectrum (HF-HRV). Low scores of these two indices are known toreflect the vagal activity and the ANS influence on the heart, whichis associated with anxiety and stress responses [16, 23, 27, 117].

5 RESULTS
5.1 Subjective anxiety analysis
5.1.1 Screening fear of water assessment questionnaire (FWAQ).
The analysis of the FWAQ confirmed that our participants (n=12)
have a fear of being in the water. We compared the mean values of
the FWAQ questions of our group (M=3.18, SD=0.68) to the meanvalues of the FWAQ fear group (M=3.47, SD=0.93) and non-feargroup (M=2.15, SD=1.08) in the validation work of the FWAQ [82](Fig. 4). We performed a T-test to understand if our group had a fearof being in the water when compared with the fear and non-feargroups of the FWAQ. We found no significant differences (p=0.176)
between the FWAQ scores of our group and the fear group of Misimi

et al. [82], and found significant differences (p=0.004) between the
FWAQ scores of our group and the non-fear group of Misimi et al.
[82].
5.1.2 Anxiety self-report. Since 2 participants did not complete
the last stage of the procedure, we analyzed the AAAQ with n=10.
Figure 5 shows the anxiety that participants reported during theprocedure’s floating stages. In general, we found lower scores of
the negative statements "I’m nervous about water" and "I’m worried about water",which could suggest lower anxiety levels during
the second floating stage. During the fourth stage (using the XR
system delivering VR experience), we found that most participants
reported lower scores in these same negative statements, which
may suggest decreased worried and nervous feelings; however, theyalso reported decreased levels of calm, relaxed, secure and comfort
feelings.
Every participant reported different levels of anxiety during thefloating stages. For example, P4 reported high scores for all thestatements in the baseline condition. After the first floating stage,
P4’s scores of calm, relaxed, secure and comfort feelings decreasedby 3 points, while their scores of worried and nervous feelings
stayed high. Moreover, during the fourth stage (using the XR systemdelivering the VR experience), the feeling of nervousness decreasedby 1 point, while the worried feeling stayed the same, suggesting a
low influence on P4’s anxiety. Finally, during the second floatingstage, P4 reported lower scores for worried and nervous feelings,
and higher scores for calm, relaxed, secure and comfort feelings,
which might suggest that the anxiety feeling decreased by theend. On the other hand, P11 experienced different levels of anxiety.
P11 also began by reporting high scores for all the statements inthe baseline condition. However, during the first floating stage,
scores for calm, relaxed, secure and comfort feelings decreasedby two points, and worried scores also reduced by two points,suggesting reduced relaxation but also anxiety. After having the
VR experience, P11 reported lower scores of worried and nervous
feelings, and higher scores for calm, relaxed, secure and comfort
feelings than after the previous stage, Which suggest that the XR
system delivering the VR experience could positively influence any

A XR floatation tank experience to reduce the fear of being in water

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

Figure 4: Results of the fear of water assessment questionnaire. Our participants showed a significant difference with thenon-fear group participating in the validation study.

Figure 5: Average scores of the ad-hoc aquatic anxiety questionnaire comparing the protocol conditions. Significant differences(*) were found in the “I feel worried about water” and “I feel nervous about water” statements.
anxiety. Finally, after the second floating stage, P11 reported thesame scores than the in previous stage for all the statements except
for the relaxed feeling, which increased by one point.
The repeated measured ANOVA test revealed significant differences between the conditions for the worried (p=0.010) andnervous (p<0.003) statements (Fig. 5). For the worried statement,a Holm post-hoc test suggested that the significant difference(Pholm=0.034) was between the second (M=2.33, SD=1.03) and

fourth stages (M=1.67, SD=0.85). Similarly, a significant difference(Pholm=0.004) was found between the second (M=2.67, SD=0.43)
and fourth stages for the nervous feeling (M=1.67, SD=0.94). Thesefindings might indicate that during the fourth stage (using the XR
system delivering the VR experience), participants’ worried andnervous feelings decreased when compared with the baseline.

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

Montoya et al.

Table 1: HRV indexes’ values during the stages of the procedure

Stage

SDNN (𝑚𝑠)Mean SD

HF (𝑚𝑠 2 )MeanSD

2nd: Baseline
3rd: First Floatation
4th: XR system
5th: Second Floatation

63.51
63.40
60.50
61.98

1174.67802.77826.711125.20

5.2

19.39
15.47
20.23
24.35

1177.40
323.06546.05964.45

Heart rate variability analysis

During the post-processing of the data, we realized some problems
with the HR sensor’s Bluetooth connection presented during thedata capture. We initially disregarded this issue because Bluetoothtends to fail if the sensor is submerged 1 meter or more. Although
in the floatation tank the sensor was only submerge approximately
10 centimetres, we had disconnection issues only detected whenprocessing the data. Therefore, for this analysis, we did not use thedata where Bluetooth issues led to incomplete data, nor the datafrom participants who did not complete the last stage. Consequently,
for each floating stage, we have fewer participants (n=9) than theoriginal sample (n=12). We compared the HRV indexes for eachcondition (Fig. 6). A repeated measurements ANOVA showed nosignificant difference between the stages (p>0.05). For both indexes,
there were two outliers in the fourth and fifth stages. All the outliers
correspond to P4, who was the participant who rated a high levelof anxiety in the AAAQ, as we discussed in the previous section.
Both indexes had the highest values in the second stage (Figure 4
and Table 2), which may suggest a calmer state when compared withthe other stages. Both indexes had lower values in the third stage,suggesting a high anxiety state when floating. Then, during thefourth stage, both indexes increased, which could be an indicationof a calmer state using the XR system delivering the VR experience
when compared with the previous stage. In the fifth stage, bothindexes increased, indicating the participants were calmer in thesecond floating floating. While the SDNN index differences did
not vary greatly, the HF did, probably because this index is moresensitive to anxiety than the SDNN [16, 23]. The indexes’ values
also indicated that contact with water evoked anxiety states inparticipants ( which could suggest fear), with values lower than thebaseline during all the floating stages. We expected this behaviour
since the participants have been exposed to something they fear.

5.3

Thematic analysis

In this subsection, we present the qualitative results showing the
UXs when interacting with the XR system. The study results suggestthat most participants (n=12) found that the XR system delivering
the VR experience was helpful to mitigate their fear of being inwater. Our data analysis identified four themes.
5.3.1 Theme one: Dive into the past: The impact of previous water
experiences. This theme comprises 48 units of data and describes
participants’ previous experiences that shaped their fear of being

in water. We found that this information provided a context to understand participants’ experiences while floating with and without
using the XR system.
At the begining, participants were prompted about their previous
experiences in water and their reasons for fear of being in water.
All participants had previous bad or uncomfortable experiences inwater, which they associated as the reason for their fear. We foundthat the scores on participants’ self-reports of fear (from 0 to 4),
and the reasons for their fear of being in water, were reflected intheir experience while floating with and without the XR system.
For example, P4 reported a score of 3 on the level of fear, and theirmain reason was the depth and lack of feeling of touching thebottom of the aquatic environment. Consequently, P4 did not enjoy
floating since the high level of fear triggered worried feelings, andfloating did not allow P4 to touch the ground. P4 explained: “I felt
like I would lose the perception of where I am, so it was difficult to letgo [of the edge] while floating, also the same for the VR”. However,other participants who rated 1 or 2 in the fear self-report, and thesame reason for fear as P4, enjoyed floating with and without the
XR system (P2, P3, P6 and P9). For example, P3 stated: “I started
focusing on my breathing, then I felt like I was floating in a slow
shallow stream, I liked that”. P1 and P8 provided another reason.
They rated 1 or 2 in the fear self-report and reported fear of being
in water because of a lack of swimming skills. We found that they
enjoyed being able to float without effort, as mentioned by P1: “I
had fun floating on [the] water without [a] life jacket”. Similarly, P11
and P12 enjoyed floating with and without the XR system, and they
rated 1 or 2 in the fear self-report and reported fear of being inwater because they had almost drowned in the past. This theme
suggests overall that the floating experience with or without the
XR system can be beneficial depending on the level of fear, and it
appears to work better for participants who self-reported moderate
fear (fear level <2).
5.3.2 Theme two: Floating Fears: Navigating the waters of anxiety
and relaxation. This theme comprises 139 data units and describes
how the floating experience, with and without using the XR systemdelivering the VR experience, influenced fear and anxiety feelings.
Eleven participants reported that floating helped them to relax
and be calm. One reason for this effect was attributed to the feelingof weightlessness provided by the buoyant water. P2 explained: “Ifelt weightless and very, very relaxed [. . . ] I think it’s the floating
feeling. It’s not a chance you’ll always get to feel it”. The buoyant
water also appeared to generate a feeling of safety. P8 explained:“I would say the reason I felt calmer was because I knew I wouldn’t
drown in the floatation tank”. Another reason for feeling relaxed was
the warm water temperature, which seemed to allow participants
to forget about the body boundaries, as reported by P9:“The time
it takes for me to lose sense of the boundary of my skin and theenvironment takes [a] long time [. . . ] but here [in the floatation tank]
it was forced - like I could reach that state in 3 to 4 minutes”. P2
explained that the lack of external sound calmed them: “at one point
I could hear my own heartbeat, that was really calming”. P8 found thatthe salt disrupted their relaxation: “The salt was getting everywhere,
which was annoying”. Interestingly, participants found that the VR
worlds enhanced the calm feeling. P2 mentioned:“Without the VR It was just me trying to calm down, but I didn’t have to make any effort

A XR floatation tank experience to reduce the fear of being in water

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

Figure 6: HRV indexes during the procedure stages. A) The standard deviation of NN intervals (SDNN, ms); B) The high frequencyof the HR spectrum (HF, 𝑚𝑠 2 ). The X marks represent the mean values in Table 1. The blue dots represent the outliers.
to do that when watching the scene”. Moreover, some participantsconsidered that floating in the tank would be a good step to gettingused to water, as P10 mentioned: “The density of the water was very
high, so the pool and ocean would be different, but this was a safe
mechanism for people to get floating and used to the water”.
Eight participants reported that the VR experience helped reduce
their anxiety and fear, articulating different reasons. Some participants mentioned that the VR environment helped them to forget
about being worried about the water, as P1 explained: “It [the VR
environment] helped me, I forget I’m in the water, the water effect adds
value to the VR experience you can feel like you are floating, I was
not scared”. Similarly, P11 mentioned the VR environment helped
to distract them: “VR definitely helped with the relaxation part, butalso a distraction to not focus on the fear”. Other participants statedthat floating using the XR system delivering the VR experience
helped them because they experienced fantasy worlds and different
interactions. For example, P3 said: “With VR, we can feel anything,
do things we cannot do, e.g., going to space, or going underwater.
With VR, we can feel it, so I think it’s great in that way”. Similarly,
P8 mentioned that the interactions in VR helped: “It makes you
interact with the water to feel comfortable with it, especially floatingin the first session; after VR, I felt more comfortable about being in
the water”. While the VR environment helped these participants,
P2 and P9 pointed out that the underwater environment increased
their anxiety feelings: “I was so scared of being underwater, like therocks and stuff, the fish was the only thing that made it okay” (P2).
Two participants reported that the XR system delivering the VRexperience did not help them and generated uncomfortable feelings.
We discovered that the origin of this discomfort appeared to be aperceived reduction of their orientation affecting their proprioception sense. In the case of P4, who had a high level of fear of being
in water, the lack of orientation in the tank space created anxiety,which increased when P4 donned the headset. They explained: “Ifelt like I would lose the perception of where I am, so it was difficult
to let go [of the edge] while floating, also the same for the VR [. . . ]I was thinking about where I was, what if I drifted away?”. P10 experienced nausea: “The VR was a bit nauseating for me, I think it’s
because I’m not used to VR and have had some problems with VR
before in the past with motion sickness”. The participants mentionedthat the VR experience could have worked better in two ways. First,
they wondered if they could initially get used to simply floating, as
mentioned by P4: “Only after when I could let go and float properly
then if I did the VR [it could’ve been ok], that [being able to float
properly] would have helped after I relaxed”. Second, they wondered
if they could first experienced the system without floating, as P10
outlined: “An intro to VR, before [being] in the floating tank, would
be good for people like me. Sometimes you have to get over the nausea
to focus on the actual message so maybe that would’ve been better
for me”.
Overall, floating without technology can provide a calm andrelaxed feeling for people with a fear of being in water. Moreover,a XR system delivering a VR environment could positively influence the fear of participants who are not sensitive to an alteredorientation affecting their proprioception sense.
5.3.3 Theme Three: Riding waves of fun: floating as an engaging
experience. In this theme, we describe the different ways participants engaged. This theme comprises 133 units of data. In general,
participants reported losing track of time, indicating engagement:“Iassumed there would be more, but it ended soon. I felt like I needed
more, I wanted a little more” (P1).
Participants reported being engaged by having fun. P10 explained: “When you let go and start floating, it’s actually fun”. Other
participants reported fun due to their interactions with the VR environment, as P1 mentioned: “The game where I had to move my headto catch water bubbles, I didn’t really have much feeling, but it was
really fun, and I was engaged in it”. Participants also described theentire experience as being “fun”. When asked about the experience
overall, P7 answered: “It was very fun”.
Moreover, participants reported being engaged by the interactions of the XR system delivering the VR experience, as P8 stated:

CHI ’24, May 11–16, 2024, Honolulu, HI, USA“I liked the interactions in the game, otherwise it becomes passive”.
Similarly, P1, who said: “The water bubbles game was nice, I could domost of the actions, the interactivity was nice”. Participants appeared
to appreciate not having to do much: “Interaction was ok, didn’t
really feel there was much” (P2). Specifically, the participants werehighly engaged in the space-psychedelic world. For example, P2
said: “The second one was really interesting, felt like meditation, thesound was soothing, it was really good”. Other participants enjoyed
the movement in the other scenes, as P8 stated: “The going up part[in the virtual world] was good”. Nonetheless, for some participants,
other interactions were confusing, especially in the sky world: “Thelast one, the cyclone one, was extremely confusing, wasn’t sure what
to do to control the cyclone” (P6).
Furthermore, participants appeared to be engaged because feelings of relaxation were facilitated, which invited such engagement.
The experience overall was relaxing for them, as P5 mentioned:“The experience as a whole: overall, it’s fantastic, it’s almost like a Bali
experience (from a relaxation point of view)”. Participants found thatusing the XR system delivering the VR experience increased theirrelaxing engagement: “The main part, I would say, VR helped with,is the relaxation part” (P11). In contrast, two participants reported
that neck fatigue interrupted their engagement, although they wereable to overcome this feeling, as P7 explained: “In the beginning, I
was a little uncomfortable, I think I was tensing my neck a lot. After
that, I felt like I was lying down on my bed. At one point, I thought I
might fall asleep, I was very relaxed”.
Participants reported being engaged by the bodily illusions theyexperienced. The bodily illusions emerged in the form of feelingmovement and forgetting they were floating in the water. As P10
explained, some of these illusions were triggered by the buoyant
water:“There was a dissonance between what I was feeling and being
in the water, like when I wasn’t paying attention to myself, I felt like
I was on my bed”. However, most of the illusions were triggered by
the VR environments. In this regard, P9 said: “When the background
was moving, my engagement in the VR was so high that I must havelost that sense that I was in the water”. Forgetting about water madeP8 feel like being in outer space: “For a very brief moment I forgotthat I was in the water [while using VR], it was like being in outerspace, but it was very brief, maybe 3 secs long”. The virtual sky world
made P2 feel like they were floating away: “It felt like I could float
away, especially the sky one, if I moved my legs, I could just go away”.
P6 appreciated how the VR experience could create these illusions:“With VR, I can see how you’d overlay interesting visual experienceson top of that feeling of weightlessness”. P9 reflected on the reasons
why these bodily illusions happened: “Your mind is trying to figureout what is there, if it’s trying too hard to figure out the visuals, thenyour mind is too engaged in it and maybe not in your surroundings[water]”.
Taken together, participants found the experience engaging
through fun feelings, the VR interactions, relaxation, and bodily
illusions. Albeit motion sickness hindered the emergence of fun for
two participants. Also, six participants reported neck fatigue dueto the headset, which “kind of clashes with the experience” (P5).

5.3.4 Theme four: Tech on the tide: navigating technology perceptions while floating. In this theme, we describe how participantsMontoya et al.

perceived their interaction with the XR technology during the experience. This theme comprised 55 units of data.
Participants enjoyed different aspects of the technology. The
virtual worlds took most of participant’s attention, and they mainly
enjoyed the visual aspects of the experience: “The visual part of it
was amazing, though I kind of just enjoyed the chill visuals” (P6). P12
concurred: “The way it [the visual] is made is very beautiful, gives a
new experience to the users”. While some participants enjoyed thesound, most of them could not hear it clearly because their ears
were submerged: “The sound wasn’t really clear, probably becauseof the water” (P11). Participants disliked the verbal and written
instructions. For example, P6 said that “The talking was a bit [disruptive], like, oh, I have to do this or that”, and P8 added that “thetext was sometimes annoying, sometimes distracting”.
The required headset adjustments emerged as an issue. While theresearchers adjusted the headset straps and focused the lenses forevery participant, some found the fit to be a problem. For example,
P7 said that “Sometimes the precision [fit of the headset] might’vebeen annoying”. While we informed the participants beforehandthat their head interactions were made to prevent the headset’s
submersion, they still expressed concerns about it. For example, P7
said: “I wasn’t sure if my head would go into the water, so I was afraid
to move my head too much. I think the alignment of [the] headset
had some issues”.

5.3.5 Theme five: Making waves: transforming willingness to performfuture water interactions. In this theme, we describe how participants reported an increased willingness to perform water activities
after the study. This theme comprises 45 units of data.
Ten participants reported that they would repeat the experience.
One of the reasons was that they found it a good progression tostart floating in a floatation tank, which is a controlled water environment: “It was a good initial experience to start off within a small
body of water without having too much fear of the water” (P10).
Participants also reported they knew they would not drown in a
floatation tank: “It was always in my mind that the water isn’t too
deep and I won’t drown, I can always touch the sides” (P2). Participants indicated that they enjoyed and would repeat the experience:“I would do it again, it [floating using XR] is fun” (P1). One participant mentioned that just floating without the system was more
appealing, and one participant was negative about repeating theexperience: “I wouldn’t like to go into a pod again. The one way thatit helps [to reduce the fear, is because] in the pool there’s company,
you can start playing, but you can’t play here. When you can play,it gets easy, maybe you were trying that with the VR, but I was too
focused on the floating” (P4).
Interestingly, eight participants stated that after the experience,
they would like to try other water experiences: “I would try again
floating on seawater, but I would still use a life jacket” (P1); “I would
like to do this again, I would like to do it without the salt, just general
floating. Initially, in a swimming pool, I’m scared of the ocean” (P11);and “Maybe I’d be more open towards floating in the sea - because
I personally can’t tread water, I’m not sure whether I can float, butmaybe with this experience I would be open to trying it more” (P5).

A XR floatation tank experience to reduce the fear of being in water

6

DISCUSSION

In this section, we will discuss our results based on the assumptions we established in the introduction, and we will also compare them with the findings of previous HCI work and WaterHCI
work. Firstly, we note that prior WaterHCI work have investigated the coming together of interactive technology and water,
mostly from the perspective of using water to offer force-feedback[30, 53, 72]. Prior work also investigated water as an interface, suchas display [76, 114]. In contrast, we extend WaterHCI by adding
knowledge on the role of interactive technology when people areinteracting with water while "in" water, i.e., immersed in water[21, 28, 34, 46, 92, 107, 126, 127]. As such, we believe that our findings will be particularly relevant to people working in this space,but might also be interesting to other WaterHCI researchers andeven researchers in other sub-fields of HCI, such as healthHCI,
people working on immersion and HCI, researchers working on
HCI issues around mixed reality.
Secondly, in the next subsections, we will discuss our study
results and their implications on the use of water playful activities
to reduce fear of water and their possible applications in otherphobias. Moreover, we highlight that as we are interested in theUXs, we wanted to begin the investigation of the coming togetherof XR, water and fear with a focus on the user experience as aholistic construct [29]. Hence, we will discuss the role of the system
as a whole. Prior work highlighted the importance of such a holistic
approach to UX in HCI, especially when it comes to novel andplayful systems [14, 15, 48, 49, 87]. This was further cemented
by research that argued that playful experiences such as our XRexperience should be seen as "one" experience where the whole isbigger than its part [15, 87].

6.1

Dive in and thrive: Introducing people towater engagement

Our study results confirmed our hypothesis relating to the use offloatation tanks as a controlled setting to introduce people with afear of being in water to a water environment. Our results suggestthat the system was successful in progressively introducing participants to water and enhancing their engagement with it. Firstly,
quantitative data from the AAAQ questionnaire revealed that participants felt less anxious while the floating experience progressedfrom the second (baseline), to the fourth (floating using the XR
system delivering the VR experience) and fifth stages (last floating),
as significant differences were found in the worried (p=0.002) andnervous (p<0.001) statements. This was aligned with the qualitative
data suggesting that, while participants had a fear of being in water,most of them enjoyed floating effortlessly and reported being calm,
knowing that the floatation tank was a safe water environment.
Additionally, participants reported that the XR system helped them
to be calm and relaxed. These findings appear to confirm previous
sports science work, where researchers progressively introduced
people to water before starting swimming lessons by helping them
float in a pool [60, 90, 110] and used water visualisations prior toentering the water [101]. Furthermore, we extend this theory bysuggesting that interactive technology, when used in water, canincrease perceived calmness in participants while exposing themto an otherwise fearful environment. Our work also suggests that

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

an interactive experience in a floatation tank could progressively
introduce people to being in water. Floatation tanks could offer
independence since there is no need for an instructor to hold theperson’s body to float in water.
The anxiety self-report scores support the subjective statementsby participants reporting feelings of fun and enjoyment. These
quantitative and qualitative findings suggest that the XR systemenhanced participants’ engagement with water through the VRinteractions, relaxation, and bodily illusions (Theme three). We
believe that this engagement led participants to report their willingness to engage in playful water activities in the future (Theme five).
The findings appear to confirm prior work that showed that people
who feel confident in water are more likely to engage in water
activities [13, 62]. Our research also extends this prior work since
we found that interactive technology could help to facilitate thisengagement. However, our results also suggest that people with afear of being in water and sensitive to an altered proprioception
sense are unlikely to engage in such water activities, since they are
negatively affected by the lack of orientation and their inability totouch the ground while floating.

6.2

Splash of courage: VR environments
combined with water to conquer water fears

Our study results appear to confirmed our assumptions that an
XR system could help participants mitigate their fear by being entertained. However, we acknowledge that this effect depends on
several factors. First, our quantitative results suggest that the useof the XR system delivering the VR environment while floating
helped to reduce most participants’ perceived fear and anxiety levels. Although the HRV indexes did not show a significant difference,
they revealed a tendency toward less anxiety in participants when
floating using the VR environment, while anxiety levels were foundto be high when participants were floating without the XR system.
These results are aligned with the qualitative data showing thatmost participants (n=8) reported that the VR experience helped
reduce their anxiety and fear (Theme 2). Additionally, results are
consistent with exposure therapy theory, which predicts that if
participants are exposed to what they fear, their anxiety increases[17, 41, 117]. Also, the lower anxiety levels in the fifth stage (lastfloating) can be explained by exposure therapy: if people are progressively exposed to what they fear, they become used to it [17, 70].
We extend this theory as our results suggest that exposing people
to their fears in a real and virtual way at the same time can havedifferent results. On the one hand, XR exposure could introduce
people to their real fear, while avoiding uncomfortable feelings byproviding a virtual version of what they fear (water visuals). On
the other hand, XR exposure could trigger more fear in comparison
to traditional exposure because the virtual exposure might makeparticipants uncomfortable due to the realism of the environments.
For two participants, the combination of floating in water with the
XR system delivering the VR experience triggered motion sickness
and disorientation, which increased their anxiety and became abarrier to their engagement.
Furthermore, contrary to most VRET systems that present visual
simulations of what is being feared to induce the fear, only one VR
world used in our study was a simulation of being in water (theCHI ’24, May 11–16, 2024, Honolulu, HI, USA

underwater world). One VR world did not simulate water at all (thespace psychedelic world), while another involved exposure to water
through virtual rain (the sky world) but no immersion in water.
According to the thematic analysis, these two worlds appeared tohelp our participants reduce their fear most. In this regard, when
exposing participants to what they fear in the real world, VR could
distract them, which might allow them to overcome the fearfulsituation.

6.3

Design strategies

We now articulate strategies to assist designers of interactive technologies for water activities to facilitate user experiences of reduced
fear of being in water. These strategies might also be valuable forresearchers interested in interactive applications for other phobias.
6.3.1 Exploit distraction through XR play. Our results suggest that
the XR system’s playful interactions could distract participants,
reducing their fearful responses. These results confirm prior theory
where swimming teachers facilitate playfulness in pools to distract
students from their fear of being in water [60, 129]. These results
also confirm prior VRET work suggesting that playful design could
help people with fear [8, 39]. Moreover, we extend both theories,
having found that interactive technology use, while exposing participants to the actual fearful element (water in our case), can also
distract people from their fear.
Design strategy: We recommend that designers consider exploiting distraction through XR play. Apart from using VR environments, designers could create interactive experiences in bodies ofwater that combine visual and auditory stimuli with the performingof a task. This could include using speakers to trigger entertaining
sounds when people go from shallow water depths to deeper parts(inspired by prior work on sonification tasks to encourage physicalactivity [65]), or using projections of relaxing visuals while people
try to let go of floatation aids. Nonetheless, if designers are going
to include entertaining visuals by means of VR headsets, they must
consider their usability, as pointed out in our findings (Theme four),confirming prior work that suggest VR headset’s usability can influence the user experience [43, 77]. Moreover, playful experiences
could also be created through storytelling, as other HCI work has
proposed [89]. As with the water spirit used in our system, providing a playful story could encourage people to confront their fearof being in water. Designers could consider co-designing systems
where participants tell their personal reasons behind their fear,
inspired by the personal stories our participants told us (see Themeone). These stories could be delivered as distractions using waterproof headphones, as prior participatory design works suggested
co-design for VRET [36]. Additionally, designers could consider
providing a companion through XR, such as a conversational agent
that guides people through their floating, talks to them, and makes
them feel safe (inspired by the water spirit). These conversational
agents have exhibited the potential to support accompaniment inother contexts, such as daily life [123], and we believe they also
have the potential for accompaniment in fearful situations.
6.3.2 Utilize XR’s ability to draw from the tactile experience of
the world. Creating a tactile experience of water is challenging invirtual worlds due to current haptic interface limitations [38, 94]. XRMontoya et al.

systems have the advantage that they can draw from the physicalworld, as our system demonstrated by using real water to create atactile experience. Our results (Theme two) suggested that despite
the participants having a tactile experience with the fearful element(water in our case), warm water made some participants realx. This
contradicts prior VRET theory arguing that fearful elements inother phobias can create a fear response through contact (such asa spider mount). In contrast, we found that the tactile experienceof water through direct contact appears to be able to reduce any
fearful response.
Design strategy: We therefore recommend that designers consider utilizing XR’s ability to draw from the tactile experience of theworld. In particular, we encourage designers to leverage the tactile
experience of water while using XR, which could be achieved withpublic swimming pools, inflatable pools, and hot springs (to further
encourage relaxation and calmness). Additionally, even if designers
employ “virtual” water and its tactile experience, they still mightneed to consider the heat that comes from it to mitigate the fear
(and can facilitate well-being according to prior work [88]). As such,designers might still benefit from employing XR that allows engagement with real water once they have considered participants’degrees of fear and understood their potential positive or negative
responses to tactile water experiences. In similar ways, designers
interested in addressing other phobias may consider mixing VRET
with the tactile experience of a related fearful situation. For example, most acrophobia (fear of heights) researchers just simulate thewind sound when creating a VR environment [44, 69, 113], however, they could consider adding the tactile feedback of the windsensation [54].
6.3.3 Utilize XR’s ability to draw from the physics of the world.
Simulating real-world situations in VR is challenging due to thedifficulty of recreating the physics of the world. Prior HCI work
has proposed technology efforts to address this [19, 52, 68]; however, these are only solutions for specific cases and are still at the
prototype stage. Hence, we find that recreating the physics of theworld is still difficult to achieve in situations such as when aiming
to help people with fears. Nevertheless, due to the reality-virtuality
combination of XR systems, they can take advantage of real-world
physics, like the XR system used in this study leveraged the water’sbuoyancy, which allowed feelings of weightlessness [84]. Without
XR, facilitating this feeling can require extensive engineering efforts, for example, see prior work that created complex structures
including harness [55]. In contrast, using buoyant water appears
to be a relatively easy way for interaction designers to achieve
weightlessness. Although our results (sections 5.1, 5.2) suggested
that the fact of being submerged in water can create anxiety feelings, we also found (Theme 2) that the buoyant water can createa safe environment for people with a fear of being in water and alack of swimming skills. Furthermore, we found that the XR system’s visualizations of outer space and the sky could amplify theweightlessness feeling in participants, increasing calm. These results extend prior work that suggested that technically amplifying
buoyancy could have benefits, such as facilitating engagement [84].
Design strategy: Taken together, we therefore recommend todesigners to consider utilizing XR’s ability to draw from the physics
of the world. For example, to take advantage of buoyancy, designers

A XR floatation tank experience to reduce the fear of being in watermight want to explore the use of physical props such as swimming
teachers do, such as analog aids (e.g., pullboys) or digital aids (e.g.,
digital inflatables). Designers might also want to consider augmenting the water’s density as is the case with floatation tanks that get
filled with Epsom salt; however, the density is fixed in natural bodies of water. Nevertheless, rather than taking on the difficult task ofchanging water’s fixed buoyancy, designers could amplify water’snatural buoyancy by using VR visualizations that could simulate
users floating or flying, for example, and make them think they
are more buoyant than they actually are. However, if interaction
designers want to use VR and buoyancy, they should be cautious
and remember that most VR engines assume a standing body. In
contrast, when a designer employs water buoyancy, their user will
most likely be in a supine position. This body-position difference
will interfere with the headset sensors and tracking will need to be
reprogrammed (as with our system).
6.3.4 Consider XR’s capacity to disrupt proprioception via sensory
mismatches in the physical and virtual world. A fear of being inwater often has to do with the loss of our sense of orientation in
space, affecting proprioception [119]. Our results are aligned withthis theory since we found that our participants with fear of being
in water became anxious when they lost the sense of orientation
when floating. Our results are also consistent with prior theory
arguing that neck proprioception shapes human body orientation[98] (participants’ necks were floating, like the rest of their body)and that, in general, low gravity environments (like water withhigh buoyancy) can affect proprioception [63]. Hence, it makes
sense that floating can affect proprioception and, as some of ourparticipants mentioned, floating may lead them to lose their senseof where they are in space (theme two). Moreover, some of ourparticipants reported motion sickness, which suggests that the XR
system amplified their loss of orientation, affecting proprioception.
These results confirm prior VR theory that argues that, as visual
stimuli are dominant in influencing proprioception, the high visual
stimuli in VR interactions influence orientation [22, 119]. However,the proprioception of the majority of participants was not affected.
Furthermore, while some lost their orientation in space, this loss did
not increase their anxiety (theme 2). In these cases, we found that
the XR system could leverage the participant’s loss of their senseof orientation in space to encourage more immersive experiences
because it appeared to become easier for them to believe that they
were in the virtual world.
Design strategy: Taken together, we recommend designers toconsider XR’s capacity to disrupt proprioception via sensory mismatches in the physical and virtual world. In particular, when combining XR and altered proprioception in water, designers should
consider two things. Firstly, designers could create (playful) interactions to introduce participants to floating and VR, especially ifthey are prone to experience a loss of the sense of orientation in
space. Secondly, designers could also provide static, non-moving
VR environments to avoid motion sickness, as was suggested inprior VR work [22]. Thirdly, designers could also create grounding mechanisms while people are floating, providing them with a(physical) anchor to help them avoid drifting or losing orientation.
Moreover, we note that XR’s capacity to disrupt proprioception
might need to be considered when designing for other fears since

CHI ’24, May 11–16, 2024, Honolulu, HI, USAa lack of awareness of one’s location in space will add to the anxiety already associated with exposure to the fearful element. For
example, people with sensitive proprioception, alongside fear ofheights or claustrophobia, may experience heightened fear if theylose their sense of their location in space.

7

EXPLORING LIMITATIONS AND CHARTING
FUTURE WATERS

We acknowledge that the length of the stages constituted a limitation of this research since the stages could have been prolonged
to provide an extended HRV recording. However, long floatation
sessions (often >1h) can trigger the “aquatic mammal reflex”, which
automatically decreases the heart rhythm and allows for relaxation[11, 37]. These changes could have interfered with our findingson the XR system’s impact. Furthermore, an extended period in a
floatation tank results in the discomfort of "pruned" skin. WaterHCI studies need to consider this effect, and the designers of futurestudies need to carefully balance data collection and user comfort
outcomes.
Moreover, we acknowledge that we investigated the impact of
the XR system as a whole, which did not provide the specific impactof each component of the system over the participant’s experiences.
As such, we follow similar work that investigated the impact of an
entire system design on people’s experiences through both qualitative and quantitative data [31, 32, 86]. Future work could investigate
particular sub-aspects of our work and provide additional understanding of how XR can support our participants. For example, we
can envision a study that involved only one VR environment at atime, or a study where participants were only immersed in VR, but
not engaged in gameplay, or a study where the water temperature
was significantly different to their body temperature. However, we
believe that our holistic approach could serve as a useful scaffolding
to such future studies to complement our work.
We also acknowledge that we have so far only investigated one
XR system. Future work might consider more systems, including
different headsets or even haptic technologies, as well as bespoke
XR experiences, to both validate and interrogate our findings. Future
work could enhance our understanding of how to design XR systems
that offer the welcoming “side-effect” of entertaining people withfears as well as those without. Such “side-effect" developments
could extend our understanding of serious games. Also, such anenhanced understanding of how to design XR systems could be
useful in future work concerned with designing for specific usergroups, including people with diagnosed phobias.
Finally, we note that our participant number is in line with similar studies in prior work [26, 75, 84, 115, 122], although we did
not find significant differences in the HRV data. Nonetheless, theanalysis of the data with a lower number of participants was madeto ensure accurate results instead of adding data that could be compromised. Then, we encourage future studies with a larger numberof participants to expand our results. We believe that our work
might be scaffolding to inform such future studies. Furthermore,
we believe that our work has value as it is the first investigation
into the use of an XR system within a floatation tank to reduce fear,hence could form a basis for future studies considering interactive
technology and the wellness industry.

CHI ’24, May 11–16, 2024, Honolulu, HI, USA

8

CONCLUSION

We presented a study evaluating the potential of an XR system tomitigate the fear of being in water. Our qualitative and quantitative
results suggested that the XR system, which combined a real water
environment (in the form of a floatation tank) and VR interactive
technology, could help people with a fear of being in water to feelcalmer and, thereby, mitigate their fearful responses. We provided
an articulation of the user experiences of people with a fear of
being in water when interacting with such an XR system and we
presented strategies for the future design of XR systems for people
with particular fears. More broadly, we hope that our work helps
HCI practitioners using interactive technology for wellbeing andWaterHCI researchers to engage people in playful water activities
and hence profit from the associated benefits.

ACKNOWLEDGMENTS
The authors would like to thank the director and staff of the floatation center Palm Ave Float Club in Singapore for allowing us to
conduct our study in their facilities and for collaborating with us.
Moreover, we would like to thank the director of the floatation center Water Temple in Melbourne for allowing us to record research
activities at their facilities. Additionally, we would like to thankall the participants who volunteered to take part in the study presented in this work. Florian ‘Floyd’ Mueller thanks the Australian
Research Council, especially DP190102068, DP200102612 and, with
Sara Jane Pell, they thank LP210200656.

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