I wade into a marsh pond and see a funny speck of dirt crawling on the surface of the water. But on the underside of the water’s surface . And it’s not dirt, but a minute snail from the family Hydrobiidae. This particular snail is not content enough to walk with its stomach foot on the ground or the plants, but to fancy itself on the underside of the water’s surface.
If you are small of mass, gravity pulls on you very weakly. If you are small enough and a snail, you can spread your stomach-foot out wide and can take advantage of the water’s surface tension to walk on the ceiling.
But first you must get to the ceiling. This minute snail can simply crawl up the side of the pond bank or a plant stem. Or create a tiny bubble of air to carry it up to the water’s surface. Often they will do this when it gets to crowded on the bottom. How nice it would be to simply create an escape bubble anytime you were uncomfortable.
I cannot walk on water, on the surface or underneath, and my legs create tsunami sized waves relative to the tiny water-walker as I walk. The snail’s grip on the surface relinquished and it sinks awkwardly to the bottom, like a coin dropped in a bucket of water. Now it must decide how comfortable it is and whether to stay on the bottom, or rise to the top.