I was a BM2(SW/SAR) in the US Navy. BM2 means Boatswain's Mate, 2nd class. (E-5 or the equivalent to a Sergeant). Pronounced "Bosun's Mate" which for some gets shortened to "Boats", a nickname that is bestowed upon Boatswain Mates that know and do their job well. It is a nickname I still carry and am called even though I have been out for a couple years.
The SAR comes from the (SW/SAR) which are additional specialties in the Navy, this one meaning Surface Warfare/Search and Rescue. The Search and Rescue swimmers in the Navy are the sea/air/land rescuers. I did maritime SAR and combat SAR. Mostly pulling downed Marines out of harms way on land, downed pilots and man overboards at sea. We were deployed via small boats, ships or helocopters.
Hence: SAR_boats