How does a water boatman swim?

Answer 1

All liquid has what is loosely called surface tension. This could be likened to the skin you get on tomato soup, except most liquid doesnt have to "go off" before it developes its skin.

Water-boatmen are so light that when they swim they do not actually penetrate the "skin" of the water. Tiny hairs on their limbs grip this "skin" in the same way the hairs on a flys' legs grip the ceiling. You could say that water-boatmen don't actually swim in water at all, but rather WALK on it!

If you want to try an experiment to test how strong the "skin" of water really is, try making yourself a cup of your favourite drink (tea for example). With the cup full, take a teaspoon and try to balance it on the rim of the cup so that the spoon end is floating in the liquid and the handle is horizontal (ish). It might take a bit of practice to get the spoons centre of gravity in exactly the right spot, but when you do you will notice that you can slowly push the spoon so that more of its weight is resting on top of the liquid. Eventually of course, the spoon will sink. This happens when it displaces a mass that is greater than its own. The same applies to water-boatmen, and all other creatures that can walk on water.

Answer 2

They fly. If you see them failry close up, they have a small set of wings and can fly. They come into the pool looking for food such as algae.