The old fashioned curved swimming snorkel, with the ping pong ball holding the tube shut by its buoyancy when the Diver submerges ...... if the ping pong balls volume is the equivalent of 33 grams of water, is that the upward force per its cross-section area (12.5 sq cm)? .... 2.5 g/sq cm? So my Idiot's Question is how do you calculate the weight or force of the water that would push the ping pong ball away from the tube opening letting water in? Is it only the weight of the water contained in the portion of the tube that's in the downward "swoop" of the upper "hook" of the snorkel? I sure hope someone understands the image of what I am describing! I actually want to 3d print a level valve lock for a hydrogen generator reservoir tank, to maintain a certain height in my system, and the simplest would be with a ball float. But I completely confused myself trying to study the principle of the snorkel air lock first. Thanks!