I owned a Poseidon in the seventies, using it for winter cold water diving. It has an inlet and exhaust on the chest. The worst thing you can do in a drysuit is work up a sweat. We used to ventilate heavily to keep from getting sweaty underwater. At times, we would blow up intentionally under a boat to wedge ourselves between the bottom of the boat and the shaft or cutlass bearing, or just to stick to the bottom of the boat. But once done with a dive, it was very relaxing to get clear of everything, and blow up while laying horizontal on the surface of the water to get the suit off your underwear, and just shake everything out. But you couldn't blow up too much, as you still had a harness on. The tender reeled you in like a bloated whale, and you'd exhaust and deflate right before climbing the ladder.
Steve