IGN asked Cameron about it last month and he replied: "Actually, it's not a question of room, it's a question of buoyancy. When Jack puts Rose on the raft, then he tries to get on the raft. He's not an idiot, he doesn't want to die. And the raft sinks and kind of flips. So it's clear that there's only enough buoyancy available for one person. So he makes a decision to let her be that person instead of taking them both down."