Feel free to read this only after you've seen the movie. If you haven't yet, you should. It was awesome.
So in the middle of the ocean, on an ocean liner, in the pool, on a floaty, a man chokes on his cocktail and dies.... This shouldn't be funny.
Watching The Dark Knight I kept experiencing a similar phenomenon. Joker--SPOILER ALERT--was in this movie. And he--SPOILER ALERT--did things. It kept happening that these things were really quite funny. But it was hard to laugh at them. One wished to--one saw the humor. But, you see, he is, the Joker--especially this one--such a sick, twisted, psychopathic bastard, that everything he did just seemed too dispicable for any half-way decent human being to find any humor in it. So I sat there, they had Joker do something on the screen, and the laughs were sort of half-assed, because we audience members were clearly embarrassed to find these things funny.
Remarkable, awesome phenomenon.