During the summer, maybe jeans, t-shirt, lifejacket - oilskins if there's a bit of spray about.
If it's cold, all in one floatation suit with 275N auto lifejacket (apparently it helps righting if you go in the water with a floatation suit).
When safety boating, I wear dry suit and bring along buoyancy aid although generally wear auto lifejacket - may get a manual one next year instead.
At work, we are required to wear lifejackets when working on or near the water, this includes on the tug.
I remember a while ago, there was a fair amount of talk when a tug turned over in the entrance channel to the dock about whether auto or manual lifejackets should be worn. If you're within the cabin doing escort work and the thing turns over before you can pull the hook, an auto-lifejacket would probably affect the speed you can get out of the cabin if it has gone off cos it could potentially pin you to a wall or something.
Don't think I'd ever wear a manual lifejacket if I was out on the boat on my own - getting knocked overboard in an unconcious state would be bad.... would rather be automatically righted than drown.