Per riverman:
When you are immersed in the water, you have neutral buoyancy...drysuit or
not, full or not, and moving water or not. If your suit is full of water,
you have much higher mass, therefore you cannot change direction, catch an
eddy, or hold on to a handhold so easily, but there shouldn't be any new
forces trying to submerge you.

I don't have any experience in moving water, but my take on a flooded dry suit
is that the two biggest problems a

- Cold. Most people don't wear neoprene under the suit, so once it's full
of water, you're practically naked. Not totally unless the suit is
flushing a lot, but close enough....

- Getting out of the water. I'd guess you can flop your torso over a boat,
but being able to lift a water-filled leg would seem impossible.


Couple years ago I read a survival story by a couple of HobieCat sailors.
They didn't even tear a seal or anything. They capsized the boat in heavy
air and, in repeated attempts to right it, managed to take in enough water
through the seals (like, I guess, when you make a fist and those little
channels open up around the wrist tendons...) that the PolarTec under the
suits became sufficiently saturated that they no longer had the strength
the clamber back up on the lower hull of the capsized catamaran. They said
that they would've been dead if a power boat hadn't finally come along.
--
PeteCresswell