Bubble covers are not required in industrial locations that are subject to frequent wash-downs....as there is both the risk of damage to the equipment, and the assumption of some sense on the part of the user. I think the same logic applies here as well.
Take a look at 406.8(B)(1) in the 2005 code. All 15 and 20 amp 125 and 250 volt receptacles installed in wet locations require "in-use" covers. Don
