The alarm was raised at 4.45pm that two men who had been diving were stuck on rocks around the western end of the bay. Wearing only lightweight wetsuits, they were exhausted from attempts to get back to the beach.
The rocks were inaccessible other than by a cliff descent, and the conditions meant a coastguard vessel or a rescue chopper couldn't be sent to the scene, Mr Metcalfe said.
With Houhora police and Department of Conservation staff from Te Paki at Tapotupotu, the Whangarei-based rescue team "scrambled" and set out on the four hour drive to Cape Reinga.
Mr Metcalfe and the Coastguard asked the Ahipara surf club to get an inflatable rescue boat (IRB) to the scene - a drive of at least 90 minutes by four surf club volunteers with two IRBs.
Night was falling when Mr Metcalfe made the call to allow two of the lifeguards to attempt to reach the stranded men. That was at 7.20pm and the SAR specialist cliff team was still on the road, three hours away.
"We wouldn't have even known until we got there if we could get ropes down and abseil that cliff.
``We knew those guys had been on those rocks for hours by then and would be in a bad way. They probably wouldn't have made it through the night.
"We knew it was within the lifeguards' capabilities and they were well trained and experienced, but we were aware so much could go wrong."
What happened next is what Mr Metcalfe described as the "one of the most dangerous and bravest" of rescues.
Anthony Walker and Thom Anderson manouevred their IRB across the sandbar and through rough seas, with less than 50 metres visibility, to near where they had glimpsed the divers in the failing light.
Getting as close as they could, Mr Walker dived in and "swam through pounding surf and huge seas to the rocks," Mr Metcalfe said.
Pummelled by the waves and currents, he went into a gut in the rocks and reached the men, managing to swim back with one of them to the boat.
He was too exhausted to make the return trip, so Mr Walker carried out the same action until the second diver was also on board.
By 8.25pm both stranded - and exprermely grateful - men were safely returned to the beach.
"I'm picking those two rescuers will downplay their part but they were incredibly brave," Mr Metcalfe said.