Members of the public ran to save a man struggling in the water at Whiritoa, Coromandel.
The man, in his early 20s, was about 100m from shore when four people noticed him getting into difficulty yesterday and swam out to help him.
It took about 20 minutes to rescue the man just after 5pm.
Intensive care paramedic Russell Clarke said by the time they got him to the beach the man was unconscious.
"When the ambulance arrived he started to get a bit more lively, although he was still pretty unwell.
"There was a lot of surf running, probably a metre, metre and a half surf, and obviously he got into a bit of trouble out the back and lucky a member of the public noticed he was in trouble .. so a group of bystanders swam out and brought him in."
He applauded the rescuers.
"It's a great effort. He was quite a big guy and he was quite exhausted by the time they got to him."
He said it was a timely reminder for people to swim within their limits.
"It was a very close call. I think 10 to 15 minutes longer it would have been a different story, totally. So he was pretty lucky that he was noticed by a member of the public that he was in trouble."
Auckland's Westpac Rescue Helicopter then flew the man in a serious condition to Waikato Hospital.
The crew also flew to a quarry in Kaiwaka, north of Auckland, to help a man who was trapped in a 30-tonne dump truck that had rolled.
Firefighters cut the man, in his 50s, free. He'd suffered multiple injuries and was flown to Auckland Hospital in a serious condition.
Also yesterday, a girl at Kawau Island was flown to Starship Hospital in a moderate condition after falling out of a top bunk while asleep.
The girl, who fell on to timber flooring, suffered multiple injuries.
The last callout of the day was out to Kawau Island just after 10pm, to help a man who had choked on a fishbone while eating snapper for dinner.
He was flown to Auckland City Hospital with minor injuries.