Undertow (2004)

The viewer has no certainty that Chris survived the drowning and now lives with his mother's parent because the narrator at this point is the younger brother who admits he is uncertain of his memories. Also, throughout the movie, the other characters mention that the younger brother has cognitive issues. Further, in the last scene, the only person to speak, apart from Chris, is the grandfather who speaks in a gentle, calming manner which reflects the only description given by Chris of the grandfather to his younger brother. The grandmother stands perfectly still like she is one dimensional which is a reflection of the younger brother's knowledge of this woman as Chris did not speak of her. It is noted that the younger brother is holding a balloon during this scene and when he pops it, the scene abruptly ends signifying that it was a daydream with as little substance as a balloon. The final piece of evidence that Chris did drown in the river is the statement at the start of the movie that the events are a recollection of the last Mann alive (I think that was their surname) indicating that only the younger brother survived (the uncle had been stabbed in the chest and unlikely to survive).