Drowning would be the worst. I hate not being able to breathe (after a really intense run, for example), and this would be that feeling times a thousand. God, even thinking about it is freaking me out. But, like Demetri Martin says, "Drowning would be horrible, but a little less horrible if right before you were really thirsty." So don't forget your salty food-stuffs on that ramshackle boat.