he got drunk and belligerent. ship's crew tried to calm him down and he started running around. he jumped over a railing from one deck to a lower deck to get away.

then he jumped another railing, but this was the edge of the ship. they think he didn't realize it and was just thinking of going to a lower deck again.

they never saw most of him again. they did a man overboard drill, tossed a life ring and did emergency 180. as they returned they saw an arm in the water and sharks around it.

either the propeller chopped him up attracting sharks, or the sharks just did the job themselves. he probably didn't survive impact anyway. they couldn't recover the arm before it disappeared beneath the waves.