Charlotte Watsford is the main antagonist of Season 2 of the Australian series, H2O: Just Add Water.
She is the new girl at Cleo, Emma and Rikki's school who develops a crush on Cleo's boyfriend, Lewis McCartney, who she later dated. However, is is revealed she is the granddaughter of Gracie, one of the three original members from the 1950s.
After learning the girls' mermaid secret, Charlotte becomes a mermaid herself and gains all three of their powers, causing Charlotte to become power-hungry and slowly becomes the girls' arch-enemy as the season progresses
