The U.S. Coast Guard suspended its search Monday night for Tristen Allen of James Island after the 18-year-old went missing this weekend while scuba diving about 13 miles southeast of Folly Beach, officials said.

The Coast Guard used helicopters, planes and boats to search more than 2,759 square miles - an area roughly the size of Charleston, Berkeley and Dorchester counties combined. Civilians also volunteered to help during the 53-hour search.

"This is a heartbreaking time for everyone involved, and we extend our deepest sympathies to Tristen Allen's family, friends and loved ones," said Capt. Ric Rodriguez, commander of Coast Guard Sector Charleston. "Decisions to end searches are among the most difficult Coast Guard members are ever forced to make, and are not ones we take lightly."

Allen was a recent graduate of the James Island Charter High School and planned to attend The Citadel in the fall.

The Coast Guard said Allen was diving with his father, Sam, around 2 p.m. Saturday on board a 22-foot Carolina skiff.

They dove to a maximum depth of 60 feet and both surfaced. The teen was attempting to remove his weight belt when he went under and was not seen again, said the Coast Guard.

Reach Matt Sartwell at 937-5590.