H2O: Just Add Water series 3
Cleo, Rikki and Lewis think they know everything there is to know about Mako Island, but when water attacks them on a full moon, they realise a new, potentially dangerous force is developing on the mysterious island. Thankfully, they find an ally in Bella, a new girl in town who reveals an equally surprising twist: she too is a mermaid with extraordinary super powers. Together, the new team face a new challenge that threatens all they know and love.