I spent a major chunk of my flying career in helicopters over the North Sea. The pilots in those wear survival suits, lifejackets and a lot of thermal gear under. They carry ELT's in a pouch on the jacket and normally flares and a strobe in a suit pocket. The jackets also have a strobe which goes onto the hood.
The passengers all wear heavier suits with re-breather units, to allow a few minutes escape time. The aircraft have at least three life rafts (S61 & AS332) as well as "pop out" flotation gear, an Adelt and two large EPIRBs. Everyone, crew and passengers has dunker training, with regular recurrency training. I talked with several pilots who had ditched and the common theme was that the evacuation rarely goes to plan, and the water temperature is absolutely stunning.
Then it happened to me: the initial shock that it is going to happen passes quickly with two crew doing their best to keep the situation from going from an emergency to a disaster. The aircraft rolled on impact with a large swell and filled in seconds. The water was so cold I struggled not to gasp and so inhale. Everyone got out safely, but, even in regular dinghy drill we all struggled to get into the rafts. Everyone was severely seasick in the rafts, and all had some symptoms of extreme cold/hypothermia when we were fished out. And it was August.
I still fly over water a lot, and since that time I have completed 19 solo, single engined crossings of the Atlantic, but you should see the kit I carry!