One of the first things I was told by the older hands on my first working bell run as bellman (3 man) was >... "never, ever, dead head the hot water pump" .....I always thought that was amusing, if you consider all the things that you might think important to tell the new guy, the highest priority was to not look like tits and piss off the deck support. And no it wasn't cold water diving.
There is another one that catches the bellman at times....that is when either diver 2 locks out as diver 1 or diver 2 comes back into the bell first. It is not unusual for the bellman to turn off the wrong hot water supply....and more importantly (and I have seen this more than once)..the bellman inadvertantly turns off the wrong gas supply...easily fixed but it does raise the blood pressures lol.