The U.S. Coast Guard says it has been searching non-stop for an 18-year-old who vanished Saturday afternoon while scuba diving about 13 miles southeast of Charleston.

Ron Plante, search and rescue controller for the U.S. Coast Guard in Charleston, said a father and son were among four people on board a 22-foot Carolina skiff between 2 and 2:15 p.m.

The father and son dove to a maximum depth of 60 feet and both surfaced, Plante said. The son was attempting to remove his weight belt when he went underwater and was not seen again.

The Coast Guard dispatched the Cutter Tarpin and a helicopter to the area within 30 minutes of receiving a call. They've since added a helicopter from Florida and expect to have a fixed-wing aircraft join the search as the drifts and currents cause the search area to become wider.

Plante said he does not know if a tether line was being used.

Several local boaters in the area aided with the search, Plante said.

The Coast Guard has declined to release the teenager's name.

Check back as more details become available.