Authorities will not release the man's name until his family has been notified.
About 2:30 a.m. Saturday, the Honolulu Fire Department responded to a missing swimmer and found a 17-foot-boat had overturned. Two men aboard swam to shore. The third man was found at 8:25 a.m. Saturday under 30 feet of water. He was not breathing and had no pulse.
"We are saddened by the loss of one of our Marines, but are deeply grateful for the efforts of the Honolulu Fire Department and Coast Guard in this matter," said Chuck Little, a Marine Corps spokesman.