This set of Skimmer photographs shows one working the surface of a low water marsh. Everything happens in split seconds because the Skimmer are fast and will twist/turn mid flight.
Above the bird lightly touches the water with his lower mandible, which is much shorter than his upper part of the bill.
Small fish can see the Skimmer and at times the surface will be filled with jumping minnows.
BTW, I have just read no one knows how fast a Skimmer works the top of the water ????