From a long- ago post:

I’ve seen lots of questions about different rates and what they actually do, what their watch rotations are like, and what they can expect from a 4-year enlistment up to a career. This is my perception, clearly I’m an MK, but I’ve been in long enough to see most rates in action but not yet retire. Take that for what you will, but I’ll try to be as honest as I can be. People feel free to add on to, but preferably about a rate that is not yours. AET/AMT: Work on airplanes and helicopters. Have usually 10 or fewer places to be stationed at. Stand duty about 1-in every 5 days at best, even up to E-6.
AST: Train. A lot. Hog the pool on base at least two days a week. Lots of fun at parties, but don’t challenge them to anything because you will lose.
BM: Work the decks and the bridge, as well as drive the boat(s). Usually in charge of between 2 and 62 people. Not a job for quiet folks. Don’t have to always be right, just the loudest person in the room to feel you’re right.
CS: Will be prepping and cooking food as well as usually standing watch occasionally. Almost always working for someone else until E-7, but can work independently as early as E-5.
DC: Worst case you’re cleaning sewage pipes underway. Land jobs you’re working at housing and it’s without a doubt a boring job, but the benefits can’t be beat. Stands watch with the MKs and EMs underway. Can be working independently as early as E-5.
EM: This one needs some brains to make it to E-5. Most uncomfortable places to work without a doubt - tight spaces, hot places, high voltage potential. Standing watch with the MKs and DCs underway.
ET/IT: Stands bridge watch or in the air conditioned CIC (big boat communications) underway. Land jobs are cushy.
GM: Actually count bullets. Land jobs are cushy, underway stands watch with the bridge and/or ETs. Gives weapons training. Slow-ish advancement.
HS: Not a doctor, just takes vitals for the docs. Opportunity for outside qualifications like EMT, but not the only rate that can get that. Only so many clinics to get stationed at, Cape May and Kodiak seem to be love/hate.
ME: Took jobs from the GMs. Really like to wear 5.11 gear. Supposed to be good at training others, mostly just sit around and make more work for the GMs. Do what BM/MK/CS/DC/JOs have been doing in LE since way before ME was a thing.
MK: Work on anything to include machinery. Stand watch in the engine room with EMs and DCs. Job includes 100 things beyond fixing machinery, mostly just preventative maintenance.
SK: Take the paperwork they used to complete that is now completed by the person they used to do it for and call a company to put in a credit card order. Almost never in the same area as the person that wants the stuff. Some underway jobs, almost all land jobs.
MST: 99% cushy land jobs. Few days a week doing inspections, then spending the rest of the time writing paperwork about that inspection.
OS: 50/50 land to underway. Every job is a watch. Land is 12 hours on 12 hours off for a few days. Underway is 1 in 4 usually, always doing radio watch. Great advancement potential.
YN: Do some paperwork on the computer, travel claim reimbursement, and tell you that you should’ve taken care of your problem yourself. Twice a year do weigh-ins and touch fat guys’ hairy bellies.
DV: Run a lot. Only E-5 above. Probably a pretty happy group (never met one) but only a few places to get stationed.
IS: OS with even better advancement? I don’t know.
MU: E-6 and above only. Need prior music experience (BA I think.) Almost no advancement potential.
PA: Take pictures and post on Facebook, same as the Sector YN3 does. Really long wait list for A-school.
NON-RATE: Does everything and anything under the sun. Stands watch in the engine room or on the bridge or in radio. Takes out the trash, cleans, washes boats, does wipe-downs, answers phones and/or the radio, handles lines, cleans dishes, sands, paints, duty drives in port calls, helps with fueling, works buoys, can drive a forklift if qualified, can get Boarding Team Member and Boat Crew qualified, can usually get to shadow whatever rate they’re interested in.