Would it be possible?

[johnbox]

I thought about it for a while, but ships are quite small compared to a castle or your usual Amnesia settings. Perhaps it would have to be a story about the ship visiting separate places and the experiences along the way and/or at each place.

i don't think ships have to be small, just take the titanic, it's probably bigger then the most castles. i know, he wrote something about old galleons.. but i think, dark old machine rooms on an empty titanic would be also an awesome and scary environment!
i remember, someone was doing a titanic mod... probably just the inside... but maybe you're able to model just a few stairs and stuff like this for the outside environment, do a very lowpoly ship model and take fog to cover it a bit.
then you have a nice new outside area, (maybe build out of planes, i would prefer blender or maya), add inside areas, invent a good story and you'll get an awesome mod o.o