There are lots of species of aquatic snails that live their whole lives in water. Some snails have pallial lungs and others have gills. For the critter in the video, the answer may well be that it breathes under water and doesn’t hold its breath at all.
ETA: If the guess of snail genus in the top video description is right, then it can’t breathe under water and would drown if it couldn’t find a surface to flip onto
