IPlus you can blow warm air into you neck seal and add buoyancy and extra warmth in an emergency situation.
NEVER, EVER blow air into a drysuit. Yes, it adds buoyamcy, but it is movable buoyancy. IF ypu get rolled over, the air will instantly move up to which ever bit of the suit is highest, if this happens to be your feet, you float upside down. This is not good for you unless you can breath water.
