pond skater 
noun
A slender predatory bug which moves quickly across the surface film of water, using its front legs for catching prey.
- Family Gerridae, suborder Heteroptera: Gerris and other genera, and many species, in particular the common European G. lacustris.
- As a child my family would take a Sunday walk down the local canal side; we'd kneel at the water's edge watching pond skaters and water beetles going about their business.
- There were leebeens, water beetles and pond skaters in the water.