Bulkhead is a generalized naval term for a wall; the floor is the deck, the ceiling the overhead. The majority of modern warships actually don't employ a double-hull configuration as it's considered superfluous. If 2000 pounds of high explosive detonate under your keel you've had it, end of story. It's much more common on civilian ships, particularly tankers, which are worried about things like grounding and rocks.
Most submarines could be argued to have a double hull, except, simply put, they don't; the exterior isn't designed to do anything more than provide a hydrodynamic shape. The hull is the interior pressure hull, which is what actually keeps water out. A very few have had true double hulls; the Typhoon did, in addition to a number of other measures like placing batteries outboard of the inner pressure hull which made it possibly the only submarine ever designed that could take a heavy torpedo and live to tell. Some of the other Russian monsters like the Oscar had double pressure hulls as well, which might or might not have helped them when faced with common aerial and shipboard ASW weapons...though almost certainly would have availed them nothing if faced with a Mark 48.