Even if the mouthpiece is in place, how can you tell that the diver is breathing, or that the airway is not already full of water? My own very strong opinion is that an unconscious diver needs to be on the surface out of the water no matter what their decompression obligation ... the belief that a convulsing diver must be held underwater until the convulsion has passed is a misconception and possibly a dangerous one in my opinion. The airway is not spasmed shut during the clonic (jerking) phase of a convulsion as is popularly believed by divers ... the mere fact that patients can survive 30 minutes in status epilepticus tells us the same thing. In addition, there are some nice animal studies that reveal a degree of inspiratory obstruction during seizures, but no expiratory obstruction which is all that matters in the diver rescue context. It follows that the clonic phase of a seizure may be a good time to bring a diver to the surface. The airway is open, but they are not breathing (and therefore not inhaling water). Expanding gas during the ascent will tend to keep water out of the airway. So long as it can escape it should do no harm. Waiting until the end of a seizure when respiration resumes with an unprotected airway may be the wrong thing to do.