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

Claire Rhiannon Holt ( born 11 June 1988 ) is an Australian actress , known for her roles as Rebekah Mikaelson in the television series The Vampire Diaries and its spinoff series The Originals , Samara Cook in Pretty Little Liars , Emma in H O : Just Add Water , and Kate in the survival horror film 47 Meters Down .