TV stations WOOD and WZZM reported the crash happened Sunday on Croton Pond in Croton Township, about 35 miles north of Grand Rapids.
Steven Grace, 41, of Shepherd died before he could be loaded onto a medical helicopter to be taken to a Grand Rapids hospital. He had been taken by ambulance from the crash area to a landing zone.
Police said it appears one of the watercraft stalled and the other collided with it, throwing the man into the water.
The death remains under investigation.