He can't sleep because she's dead. He misses her. Flashback in dream sequence..yada yada.
I suppose it's a little silly that I would insinuate that she dies in a shipwreck. But, it's better than my 2nd choice: eaten by alligators.
Besides, I had no "eaten by alligators" audio clip, so the flimsy shipwreck storyline will have to do. =]