Don't forget about the seasick thing....I get seasick. I think for someone who gets seasick, a submarine would be better. On a sub, the only time you have to deal with seasickness is when on the surface in choppy or worse seas, which isn't very often, except for going in and out of port. I was on a sub and a tender; when the tender was at sea I usually felt a little rough in all but the calmest of seas. When the sub was at sea at normal cruise depth, which was 98% of the time, I felt AOK. The tender didn't go out to sea too often, so I was ok there. I think I would have been miserable on a cruiser or even a carrier possibly; they go out to see for 6months or more.
Plus when you are going in and out of port on the sub (called the maneuvering watch), you have a special station to be on, and everybody on the sub has to be awake/alert/on the job. I would go to my station and just lay there and puke/drool for the next 12 hours, so I had an excellent excuse to be laying around on the job. I could get up and do something just barely if I had to, but if nothing was going on, which was 95% of the time where I was, I'd be lying down with my face pointed torwards the bilge drooling.