Even if he didn't drown, he wouldn't have made it. If you remember, only two people at most could survive in the end. And given what happened to the others, he went off easy.

They needed a post climax scare, what better way to do it then make believe that the drowned guy actually didnt drown aaaaand BOOO, scary face, oh it was a dream, yawn.

Any last words ?
Shut the beep up
-Mutant Chronicles-

Why was his death so lame? In a gory horror film you don't want to see people die by drowning off screen.

In the book I read before it came out he lived. ironic, since he wasn't really a swimmer. He was rescued by the ship that rescued Baker and Foster.

Let's see after we see him get knocked off the space in the railing, he falls into the ocean and drowns. There really isn't much to show unless you wanted to see a minute or so of Curtis getting thrown about by the waves, getting water repeatedly thrown into his mouth by the motions of the waves as he struggles and breathes, and then finally passes out and drowns.
Welcome to my Nightmare- Freddy Krueger

Generally speaking, people who fall off of ships in bad storms tend to die.

Yep, they show him get washed overboard in the storm
"A naked American man stole my balloons".
An American Werewolf In London

he falls off the ship.