All watercraft inside of structures in "deep" water are decaying, regardless of if they are protected or not. Moonpools with floors, no floors, all with roofs, are not protecting water craft from decay.
Both boat types and both sub types are subject to deep water decay even when fully enclosed. (So 3 hours, no matter vehicle type.)
Anything over 1.5 to 2 walls(+foundation) deep in water is apparently deep water.
Server: Pure
