Title: List of H2O: Just Add Water episodes
Content:  Emma Gilbert (Claire Holt), Cleo Sertori (Phoebe Tonkin) and Rikki Chadwick (Cariba Heine) are three teenage girls who become stranded on the mysterious Mako Island. When they enter an underground pool of water that leads to the ocean they find themselves bathed in the glow of moonlight from overhead. After being rescued the girls return to their normal lives but soon discover they have changed: seconds after contact with water they transform into mermaids. After further experimentation, they discover they also have unique supernatural powers over water. Emma can freeze water, Cleo can control the shape and volume of water, and Rikki can boil water. The girls enlist 
Title: List of H2O: Just Add Water episodes
Content:  The third series begins with Cleo and Rikki dealing with the loss of Emma who is travelling the world with her family. New characters are introduced including Bella Hartley (Indiana Evans), a singer and mermaid since the age of nine with the power to turn water into gelatine; and Will Benjamin (Luke Mitchell), a skilled diver who is trying to figure out the secrets of Mako Island and who accidentally seems to unleash a powerful force which turns water against the mermaids. The girls must also deal with Zane, who attempts to exploit the moon pool after Rikki breaks up with him.
Title: H2O: Just Add Water
Content:  H2O: Just Add Water, also known as H2O, is an Australian fantasy teen drama created by Jonathan M. Shiff. It first screened on Australia's Network Ten and runs in syndication on channels in over 120 countries and has a worldwide audience of more than 250 million. It was filmed on location at Sea World and other locations on the Gold Coast. The show revolves around three teenage girls facing everyday teen problems with an added twist: they are mermaids with powers over water. Only two series with a total of 52 episodes were originally planned, but due to popular demand, a third series was filmed. Series one premiered in July 2006, followed by series two in September 2007. Series three first aired in the United Kingdom in October 2009, with the Australian premiere occurring in May 2010.
Title: Claire Holt
Content:  In 2006, Holt won the role of Emma Gilbert in the Network Ten children's television show H2O: Just Add Water. The show has earned a Logie Award and Nickelodeon Australia Kids' Choice Award. While the series was renewed for a third series, Holt left the show after series two after signing on for the sequel to the 2007 film The Messengers, titled Messengers 2: The Scarecrow. She was replaced by Indiana Evans' character, Bella. Filming of Messengers 2 took place in Sofia throughout 2008. Starring alongside Norman Reedus and Heather Stephens, the film was released 21 July 2009 straight-to-DVD. In addition to television and film roles, Holt has appeared in advertisements for Dreamworld, Sizzler, and Queensland Lifesaving. BuddyTV ranked her number 55 
Title: H2O: Just Add Water
Content: Cariba Heine as Rikki, the new girl in town at the start of the show, who tends to be aloof and rebellious. Her power is the ability to control heat in water, ranging from warming to boiling, which eventually grows to allow her to control fire and lightning. Heine appears in all series of the show, and makes a special guest appearance in the spin-off series Mako: Island of Secrets. ; Claire Holt as Emma (series 1–2), who has a confident and responsible, if somewhat controlling, personality. She has the ability to freeze water, and later develops the ability to 
Title: Ema Kogure
Content: H2O: Just Add Water (Charlotte Watsford) ; ER Season 12, Episode 252 (Sidney) 
Title: H2O: Just Add Water
Content:  time. She permanently loses her abilities after a confrontation with the trio. She does not return in series three. ; Craig Horner as Ash (series 2), a keen equestrian and riding coach who appears during series two. He forms a relationship with Emma, but does not learn of her being a mermaid until the season finale, when Emma reveals her identity. Horner does not appear in series three due to filming Legend of the Seeker. ; Penni Gray as Sam Sertori (née Roberts) (series 3), Don's second wife and Cleo and Kim's stepmother who works for the National Park association. In "Valentine's Day", she inspects one of Don's boats, but is drawn into an argument between Kim and Cleo when 
Title: Claire Holt
Content:  Claire Rhiannon Serenity Holt (born 11 June 1988) is an Australian-American actress and model, who is known for her roles as Emma Gilbert in H2O: Just Add Water, Samara Cook in Pretty Little Liars, Rebekah Mikaelson in The Vampire Diaries, and its spinoff series The Originals and Kate in the 2017 survival horror film, 47 Meters Down.
Title: H2O: Just Add Water
Content:  They divorced prior to the events of series 2. ; Trent Sullivan as Elliot (series 1–2), Emma's younger brother. ; Jamie Timony as Nate, one of Zane's friends. ; Brittany Byrnes as Charlotte (series 2), the new girl who becomes the main antagonist of series two. She enjoys the arts and sciences, but can be controlling and manipulative. She comes into conflict with the girls, especially Cleo, when she begins to date Lewis subsequent to his break-up with Cleo. Upon transforming into a mermaid, she obtains all of the girls' collective powers - clarified as being due to the fact that she was exposed to the transformation conditions on her own rather than the original three being present at the 
Title: List of H2O: Just Add Water episodes
Content:  A full moon, in conjunction with a rare planetary alignment, calls the girls to the moon pool at Mako Island where their powers are greatly augmented and strengthened. The second series revolves around the arrival of a new girl, Charlotte Watsford (Brittany Byrnes), who moves into the area and develops an instant attraction to Lewis. After Charlotte sees a film of her grandmother Gracie as a mermaid she meets Max Hamilton (Martin Vaughan) who was once romantically involved with Gracie. Happy to have met his lover's granddaughter, he tells her about the previous mermaids—Louise, Julia, and Gracie—and of Mako Island. Charlotte travels to the moon pool during a full moon and becomes the fourth mermaid in possession of all the girls' powers. Believing herself superior, she and the girls become sworn enemies. This 

Question: who played emma in h2o just add water?
Answer: Claire Rhiannon Holt.