Several actors in this show made brief appearances in H2O: Meninas Sereias (2006) including Gemma Forsyth, Lucy Fry, and Dominic Deutscher.
Due a mess up with licenses the second half of season 2 has been added to Netflix as season 3.
During the casting process for the first season, 500 actresses auditioned for the three mermaid leads. The roles eventually went to Lucy Fry, Ivy Latimer, and Amy Ruffle.
In the series finale of H2O: Meninas Sereias (2006), at the graduation ceremony, right before they call Bella onto the stage, they call forth Lucy Fry (played by Lucy Fry).
Lucy Fry is the third mermaid from an 'H2O' series to subsequently play a vampire (Princess Vasilisa "Lissa" Dragomir in Academia de Vampiros: O Beijo das Sombras (2014)). Claire Holt also portrayed original vampire Rebekah Mikaelson in Diários de um Vampiro (2009) and then in its spin-off Os Originais (2013) along with Phoebe Tonkin (Hayley) who gets turned into a hybrid Vampire/Werewolf.