Water Strider / Pond Skater
Pond skaters (also known as water striders) 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 pond skaters row across the surface of the water using a long pair of legs, with the other legs behaving like ice skates.
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.
The movement of pond skaters on the surface of a pond is related to the Cheerios effect, whereby objects floating on water tend to clump together due to surface tension.
Further Information
For more information, see this BBC article.