A deck ape is the term used in the Navy for an undesignated seaman, NOT a Boatswain's Mate.
Boatswain's Mate is an actual RATE what other branches call an MOS (Military Occupational Specialty). Undesignated seamen are the non rated losers E-3 and below that work for the Boatswain's Mates.
I do feel the need that Boatswain's Mates do start off as Deck apes who train on the job, since their is no "A" School for their rate. Why would those imbeciles need a school? You don't need a class for paint chipping. So a Boatswain's Mate is a former deck ape on a power trip.
I had to work with that fucking Deck ape for three months when I was mess cranking, what a worthless piece of shit!