If you are not familiar with the “They Both Could Have Fit” argument, Vulture would point you to this helpful photo reenactment or to the last twenty minutes of Titanic, in which it is perfectly clear to anyone with a basic understanding of spacial relations that the plank in question had room for Rose and Jack. Jack’s death was senseless! They both could have died as old ladies, warm in their beds — or so the theory went, until James Cameron shot it down with a little thing called physics. Hear him out (around the 4:30 mark):
“It’s not a question of room; it’s a question of buoyancy. Jack puts Rose on the raft, then he gets on the raft — He’s not an idiot; he doesn’t want to die — and then the raft sinks. So it’s clear that there’s really only enough buoyancy available for one person. So, he makes a decision to let her be that person.”
Mythbusters is apparently devoting an episode to this very complaint, should you actually want to believe in science, rather than the power of love. Up to you.