I read once that, when you were stationed on an Ammunition supply vessel, you slept well; knowing if you were hit, you would never make it to the water alive.
On any other supply vessel, you didn't sleep so well.
Same sort of thing if you were a merchant marine sailor shipping out on a gasoline tanker.
Used to work with a semi-retired British Petroleum tanker captain. Well, he was retired from the shipping industry, just couldn't sit still so he kept working, well into his 70's, on barbwire crews on the prairies (of all things). It was a physically tough summer job in my 20's, and this salty old Brit could keep up with any of us.
Anyway, with hard work and the prairie sun baking our brains, every now and then work just sort of ceased to happen as we hydrated and swapped stories. The old captain talked about his stint with BP running tankers full of Napalm to Vietnam on the QT.
The US military was not keen on shipping Napalm bombs loaded up, so the canisters went on standard cargo ships, and the goo juice was delivered by BP. The thing about Napalm, is that it's jellied, not a liquid. To pump it on and off the ship, it had to be heated up and melted. The ship itself was customized with heating coils inside the tanker hold to accomplish this for offloading. As the ships's captain, he was bound by international customs law, and BP policy, to remain on-board to supervise both the loading and unloading of the ship.
For safety reasons, the US wouldn't let him actually dock in Vietnam - he would anchor offshore and load tenders who would shuttle smaller amounts to shore. The whole process would take a day and a half to two days to unload a topped up tanker.
I asked him how spooky it was, and he sort of shrugged, and said something along the lines of "If the sea wants to take you, she'll take you. And at least the weather in the South Pacific beat the hell out of the North Atlantic."
Vaguely related, I once asked him why he retired to an acreage on the Alberta prairie: "So I never have to see the ocean again."