I saw this movie years ago and have never managed to find it since.
Its about two boys, maybe brothers. One is either really geeky and/or partially physically disabled. The geeky one like to hold his breath under water while the other times him. Then they meet a girl where the other boy falls for her and because the geeky kid is then alone, he either almost drowns or does drown.
Please help me for my sanity
Is it possibly Simon Birch? In that movie, Simon Birch is a kind of midget who never should have survived infancy. In the end he saves a bus full of kids from drowning in a lake, but then later dies in the hospital.
It’s “inspired by” the John Irving novel A Prayer for Owen Meany, which is very good and (IMHO) much much better than the movie.