Several Water Skaters were quickly skating across the surface of the pond searching for little insects and one seemed to be very interested in the floating mayfly.  Mayflies spend most of their life which could be up to three years, under water as nymphs until they are fully grown,  then they go to the water surface and cast off their nymphal skin.  When they are able to fly, they cast off their skin again and live for no more than four days later.  I am unsure if it was a cast off skin or the actual Mayfly.