By the way grumbler, how much sleep would you normally get when in the navy? To me it seems strange with all the sleep deprivation, is that some kind of naturalisation or something?
That depends. Even at sea, when in the normal training cycle, it would be possible to get seven or eight hours of sleep in a couple of shifts, because you are in three watches - you'd spend eight hours a day on watch, maybe four or five on maintenance or training, and then have eleven or twelve hours for sleep, eating, etc. When deployed, though, you'd just as often as not be on watch twelve hours as day (because you are manning weapons systems as well as seakeeping stations) and still have four hours a day for administrative and maintenance stuff. That leaves eight hours to eat and sleep, etc. You'd be lucky to get six hours a day. After a few day's of that you'd catch a lot of colds, get seasick easily, and feel miserable all the time. A good XO would make sure you scheduled "stand down" days every five or six days when there would be no maintenance and everyone could catch a few extra hours of Zs. Those were godsends. Port visits even more so, because you'd need far fewer people on watch.
You get used to being tired all the time, but you never like it. All in all, though, I really liked sea duty.