The National Park Service is searching for a 23-year-old North Las Vegas man last seen in the water about a mile north of Cottonwood Cove on Lake Mohave on Sunday.
At 3:35 p.m, the Lake Mead National Recreation Area Interagency Communication Center received a report that a man went into the water and did not surface.
Witnesses said the man and two others jumped off a boat to go swimming and the boat drifted away.
Passengers on the boat were able to rescue two swimmers, but the third was not found. The missing man was not wearing a life jacket.
There have been three presumed drownings at Lake Mead National Recreation Area this year, and 114 betwen 2000 and 2012.