Per request from inselpeter in WordPlay

Nautical Terms:

Walls --- transverse members of the ribs between the double bottoms.

Ceiling -- The inner hull; the inner part of the double bottoms. Generally not watertight.

Door -- An opening through a bulkhead.

Hatch -- An opening through a deck.

Manhole -- An opening through a hatch.

Quiz question:
Where are the head lights on a ship?