A better ending
I know plot twists at the end of movies have become overused to the point of becoming clichés, but this film needed a bit of a lift towards the end to stop it going bland.
*SPOILERS AHEAD*
My idea of a twist here is that when the fiancé shows up at the house, the small boy who almost drowned starts talking about the accident and how he saw Elly walk into the water (to obviously drown herself.. a bitter ending is better than endless bitterness) and how he went after her to try to save her.