Ocean Safety and emergency crews responded to a swimmer in distress in Kapolei Wednesday afternoon.
The incident happened at around 12:30 p.m. at Ko Olina Lagoon 4.
The swimmer, a 71-year-old man visiting from California, was reported to be on a boogie board when he got into trouble, Honolulu Emergency Services Department spokeswoman Shayne Enright said in a news release.
Bystanders helped the man get to shore where lifeguards administered CPR. EMS crews also treated him with advanced treatment.
He was transported to a hospital in critical condition.