As title says, this film was shown regularly on one of the Sky Movies channels in the UK from 2002-2004, but I think it was an American film.
It was a standard coming-of-age film about a girl (I think her name was Krista, but I could be misremembering) and it was the year of her thirteenth summer. I think she might have been at summer camp?
The main part that I remember is that a boy was interested in her, but because he was considered the ‘weird kid,’ she found his interest irritating/would not be good for her social life. One day they go to the beach together, and go swimming. Whilst in the water, a storm suddenly picks up, and the boy ensures that the girl gets safely on a rock/the shore. In the process, the boy ends up drowning (the image is similar to Sam struggling in the water at the end of Fellowship of the Ring). This is the image that has been burned on my mind for the years that I’ve been trying to remember.