Two American civilian employees of the U.S. military drowned Thursday while swimming in rough seas off Okinawa, police said.

The two were identified as 41-year-old Robert Ashbaugh and 54-year-old Kenneth Williams, both employees at Kadena Air Base on Okinawa island, according to Okinawa Prefectural Police spokesman Takaji Haneji.

Haneji said he did not know the Americans' hometowns.

Ashbaugh and Williams were swimming with a friend, Paul Townsend, to a popular scuba diving area 50 meters offshore near the village of Onnason, the spokesman said.

They ran into high waves and decided to turn back, though only Townsend, a civilian engineer also based at Kadena, made it to the shore, Haneji said.

The three had oxygen tanks with them but were not using them at the time.

The men's bodies were taken to a U.S. military hospital to undergo autopsies, Haneji said.