## 3 Research Methodology  
This section describes the research methodology followed in this paper, which focuses mainly on the collection of information sources related to existing research gaps of the semantic modeling and simulation of cybersecurity and interoperability on the IoUT, as well as the formalization of information to be extracted. The research was conducted in a period of six months, examining academic articles, relevant literature and Web resources published between 2016 and 2022 (6 years) and it was accomplished in four steps, as depicted in Figure 4: (a) research design, (b) research conduction, (c) experimentation with tools, (d) conclusions. Regarding the research on simulation methods, the focus was on methods that facilitate the prediction of outcome of an operation before it happens, by entering data in a simulation/prediction software. Additionally, new trends in simulation technology, i.e., digital twins, were included. In order to extract detailed information through current literature regarding the abovementioned concerns, we employed the PRISMA methodology. Therefore, we formed two primary and one secondary research questions as follows. Primary questions:  
1. What are the current semantic modeling and simulation approaches regarding interoperability in the IoUT? (Figure 5). 2. What are the current semantic modeling and simulation approaches regarding cybersecurity in the IoUT? (Figure 6). 3. How can related research problems be overcome using new technologies, such as the technology of digital twins?Figure 4: Steps of conducted research. Figure 5: PRISMA flowchart of first primary question. With the aim to present existing methods and tools of semantic modeling and simulation for cybersecurity and interoperability on IoUT, a detailed review through existing literature has been conducted on general search engines (Google/Bing) and on academic Web portals such as Scopus, Google/Semantic Scholar, and ResearchGate. The specific search terms (keywords) used in combinations were:  
* internet of underwater things
* semantic modeling
* ontology
* open source
* simulation tools
* underwater network
* underwater environment and communication
* wireless communication
* unmanned underwater vehicle
* autonomous underwater vehicle
* swarm
* interoperability
* cybersecurity
* cyber threats
* risk assessment
* threat and vulnerability modeling
* search-and-rescue operation
* communication standardization
* digital twins  
Selection/rejection of literature was carried out based on specific inclusion/exclusion criteria, in order to filter yielded results from above questions, and to extract the most relevant data. Figure 6: PRISMA flowchart of second primary question. * **Inclusion Criteria** IC1. Articles presenting simulation approaches with desired and undesired results. IC2. Articles related to each research question separately. IC3. Articles related to interoperability and cybersecurity in IoUT. IC4. Articles related to the abovementioned specific keywords. * **Exclusion Criteria** EC1. Articles written in non-English language. EC2. Articles published before 2016. EC3. Articles referring to cybersecurity methods that cannot be applied in IoUT. Moreover, to provide solely open-source, non-obsolete and with specific requirements simulation tools, we employed several sub-criteria, as described in [57; 58]. Table 1 provide an overview of these general sub-criteria, distinct for underwater and cybersecurity domains. As depicted in Figures 5 and 6, in order to extract information which answers the selected research questions, we gathered numerous and various reviews, regulations, conference papers, reports and online blogs. The obtained results were filtered based on their content by using the above-mentioned keywords. Finally, in this review, the presented knowledge emerges solely from open resources related to the semantic knowledge and cybersecurity topics.