Why?

A man in blue swim trunks stands on a sandy shore as a motorboat approaches, then suddenly accelerates and creates a large wake, knocking him backward into the water. Two other men stand nearby, one in a red shirt on the boat and another in dark swim trunks on the shore, while a woman in a bikini lies on the sand in the foreground, smiling as the man falls. The scene takes place on a calm lake with rolling hills in the background under a partly cloudy sky.