I had a recent experience with what I found out by google were backswimmers.

I had always thought when they were in the pool it was a sign I needed to shock. However this year, my FC is holding steady with no CC and I still have some.

I was in the pool this weekend and ran into a particularly large (compared to the other 3 or 4) one and was able to get him splashed out onto the pool deck. I then flicked him with my finger, sending him about 8' away into our wood fence. A few moments later, he hopped back into view, and we had a stare down. Then he freaked me out. He took off into the air like a rocket!

I turned to the pool, expecting to see him splash down, thinking he had jumped, but he disappeared. In the info I found on google, apparantly their oar like "legs" are actually wings, and these and other common water insects all can fly. They are also predators, and use their beak to pierce the skin of their prey then inject digestive fluids into them, then suck the contents dry. Apparantly they can also bite humans. They can stay underwater for hours, but need to breath air. If you see them at the surface, they are either breathing, hunting, or a combination thereof

I'd been letting them slide, but they all die from now on