H2O : Just add Water, Season 2
Zane hears of treasure under the ocean and enlists Rikki to help find it, after all a mermaid can search the bottom of the ocean pretty fast. Rikki is reluctant until she discovers her dad is having trouble paying the bills - and they might be forced to move. Rikki gets Emma and Cleo to help, but conceals her true reasons for wanting the treasure.