Pond skaters are quite common and are easily seen in the UK and elsewhere. They sit on the surface of ponds supported on superhydrophobic legs with which they can propel themselves rapidly. They eat insects trapped at the surface of the pond by the surface tension of the water.
Recent research has shown that they row across the surface of the water using a long pair of legs with the other legs behaving like ice skates (for more information see this BBC article and click here for the latest research at MIT).
The weight of the water strider distorts the water surface around its feet, making a strange shadow and providing the upward force to hold it above the surface; if the water is polluted and the surface tension reduced they would sink. Pond skaters can jump from the surface of the water as if it were a trampoline.
Further details can be found on Wikipedia here.