Would be interesting to see just HOW MUCH BETTER ....A surface Dry suit would be.
Having Dived for many years,and having had close friends survive adrift at Sea for many many hours in Neoprene Diveing type Drysuits...who were subsequently rescued.
I know how with the right layers of underclothing how effective they can be!....but I don't know of any tests done with The type of Surface Dry suits we would use Boating.
One thing is for sure!!...if you find yourself having a sudden COLD WATER immersion experience...if your not wearing a Dry Suit...
you'll wish you were