Mako: Island of Secrets (international title Mako Mermaids: An H2O Adventure) is the spin-off series of H2O: Just Add Water. Zac Blakely is played by Chai Romruen, Erik is played by Alex Cubis and the mermaids are played by Isabel Durant, Allie Bertram, Lucy Fry, Ivy Latimer, and Amy Ruffle. Mako Mermaids series 1 was originally planned as a prequel to H2O: Just Add Water but as season two developed, the creator of the show decided it would actually be a sequel. Rikki Chadwick from "H2O" appeared in the final two episodes of series 3.