Well I'd assume Joker was lying and that each boat actually controlled their own bomb to fuck with the ones who didn't press the button, because who would believe they didn't press it? It would cause so much more chaos that way (actually max chaos might be to rig both buttons to blow up the prisoners, though I could also see reasons for him to rig up both to blow up the civilians).

I'm not even sure I'd be on the boat in the first place, though it's easy to say that in hindsight, knowing how things turn out. I'd probably have made every effort to gtfo of Gotham earlier than that if I could.

But for an answer that doesn't completely sidestep the question, I don't know. It's a prisoner's dilemma and I know the optimal solution is if both sides trust each other, but I'd also have a hard time trusting both the other prisoner as well as the "guards" (in this case Joker) setting up the whole situation, knowing there's no reason they need to be honest about the outcomes of each choice. Like even in the movie, Joker was going to just blow up at least one of the boats anyways when neither of them pressed the button.

Best bet would probably be to go for a swim.

What about you?