17-year-old kayaker saved after spending 12 hours clinging to kayak overnight

A 17-year-old kayaker has been rescued after separating from his high school paddling team when he capsized and was forced to tread water for over 12 hours before being rescued, the U.S. Coast Guard said.

“Coast Guard Sector Honolulu watchstanders were notified by Honolulu Fire Department personnel at 7:27 p.m. Wednesday that a 17-year-old boy had gotten separated from his high school paddling team approximately one-half mile south of Sheraton Waikiki Beach Resort,” according to a statement from the U.S. Coast Guard released on Thursday. “The teenager had reportedly capsized on a 20-foot surf ski and was not wearing a life jacket.”

Sector Honolulu watchstanders issued an urgent maritime information broadcast, launched an MH-65 Dolphin helicopter and HC-130 Hercules airplane crews from Coast Guard Air Station Barbers Point, and launched a 45-foot Response Boat-Medium crew from Coast Guard Station Honolulu to search for the missing teen.

Hours later, however, the U.S. Coast Guard released video of the 17-year-old kayaker being rescued after spending nearly 12 hours in the water clinging to his kayak in waters off Oahu's south shore after a U.S. Coast Guard aircraft spotted him around 4:20 a.m. on Thursday morning and marked off the area with flares when an off-duty lifeguard who had been searching for him finally reached him by boat.

“At 5:25 a.m., the off-duty lifeguard transported the 17-year-old to Emergency Medical Services personnel at Ala Wai Harbor, where he was treated for injuries and hypothermia and transported to an area emergency room,” officials said. “He was in serious but stable condition.”

The off-duty lifeguard who reached him said in a press conference that the teen told him he spent the time treading water and using the kayak as a kickboard trying to make his way back to shore, but the current was too strong.

The rescuer also mentioned that the boy was in shock and unemotional and said, "I was actually crying my guts out because he was okay” and that the boy told him he was worried about his mother "because she probably missed me."

The U.S. Coast Guard said many different people helped rescue the teen, including the Coast Guard Air Station Barbers Point, Coast Guard Sector Honolulu, Coast Guard Station Honolulu, Honolulu Fire Department helicopter and boat crews, Honolulu Ocean Safety Department, Honolulu Airport Fire Rescue and Honolulu Emergency Medical Services.

ABC News' Marilyn Heck contributed to this report.