warning warning WARNING
Boatswains Mates do deck and small boat seamanship, real sailor men but not overly high on the respect totem pole. Many guys end up as BMs after not making it through schools or not knowing what they really want to do. However, can be one of the most exciting rates (Rate = Job, rating = rank) But you also do a lot of the grunt work. Bosuns are also often responsible for the maintenance of the outside of the ship. But mostly a no-tech job.
Gunners Mates, if you like guns this is the rate for you. These are the pull the trigger guys. Get a could mechanical background.
Master -at-Arms = police and law enforcement work.
"fire man" is a choice you may not be wanting to make, and you definitely don't want to put it on a dream sheet if you aren't sure EXACTLY what it means. Fireman Recruit, Fireman Apprentice and Fireman are the E-1, E-2 and E-3, the lowest ranking members of the ENGINEERING rates. These are not firefighters as a primary job. They do the grunt work in the enginerooms, fire(boiler) rooms. Depending on the ship and it's operating activities, may put more hours in on watch running the ships hot and sweat inducing machinery. And they occasionally are allowed up to look at the sky. The career path is up to Electricians Mates, Machinist Mates, Boiler Technicians, Hull Maintenance Technicians, etc. In other words, putting Fireman on your dream sheet may be the first step on a path you don't want to take. You want to learn welding, metal working, air conditioning, running generator sets, turbines, etc. This is the way to go. Pit Snipes are generally well respected in that they put in longer and harder hours than almost anybody else, but are not necessarily thought of as masterminds. On a par with Bosuns.
Now if you want to be a Firefighter, get the right rate name. The rates I listed above, HTs (Hull Maintenance Technicians) MRs - (Machinery Repairmen) have probably been consolidated into new rate families. The Navy has been consolidating it's job families and it's been a while since I looked up what is what now.
Just don't want you to get a rude surprise.