Film Question

[Mr D Black]

I remember seeing a film, maybe a tv movie, on bbc1 about 16 years ago. The plot was similar to Poison Ivy with Drew Barrymore. In this film, the young teenager ingratiated herself with the local community (I think she was being adopted) and befriended another girl. The girl knows the new girl is up to no good, but no-one will believe her. I think the mischievioius girl tries to kill the other girl in a boating accident/drowning incident at sea towards the end, but the dad of the girl figures her out to save his daughter. The bad girl dies.

I'd be surprised if anyone knows this, butit was a good film.