A 34-year-old woman was found unresponsive about 100 yards off Makua Beach Wednesday.
Honolulu Ocean Safety crews found the snorkeler just after 9 a.m.
“Lifeguards responded by paddleboard and rescue watercraft and boarded the tour boat the patient was with,” according to Honolulu Emergency Services Department spokeswoman Shayne Enright.
Lifeguards and boat staff performed CPR before the woman was brought to shore.
She was transported to a hospital in critical condition.