Coast Guard specific
Life afloat has it's ups and downs. First, your social life, and general fashion sense will suffer. You get into the routine...watch schedules, the most feared of which is "Double 4-8s." When you're not on watch or working on your qualifications, you're performing your collateral duties.
You may have a division to run, I had a few divisions while on my ship. I had the bridge BMs, ETs, IT, and OSs (everyone the operations officer had, only I worked for the operations officer).
Coast Guard cutter crews are tight, small groups. Everyone knows everyone. Sometimes that's good, sometimes it causes from friction.
Patrol tempos all depend on where you are. When we were on North Atlantic patrols (D1 patrols) we basically set our own schedules. We did a lot of boardings, but once the sun went down, provided there was not a high interest vessel or a SAR case, it would slow down a bit for the night (besides the fact that you're drivng near other vessels).
In a south patrol things was far less predictable. While we had full days of boardings in the north, a south patrol could results in days of cutting holes in the ocean. When things did pick up, you knew not to make plans. On our way to interdict a boat load of Cuban migrants we would come across other boat loads. One day I had watch mid-morning on the bridge, processed migrants in the afternoon and interdicted a boat, had a late night, LONG interdiction, and then went back on watch for my night watch.
4-5 hours of sleep was normal.
Rough seas, the constant pounding of the ocean, interesting sleep schedules, are all part of it. Time will craw each day, but the days will tick down.
As a JO in the Coast Guard you will have far more collateral duties than your Navy counterparts (something I didn't realize until I went to a joint USCG/USN school in Mayport, FL), but that will teach you to judge more than one major task at a time.
You will enjoy your few port calls.