The volunteer patrol that was on duty had been packing up for the day when they got the call that a boat had capsized with 11 people on board.

Muriwai volunteer patrol captain Brett Hardie says they'd already put the boats down so they put them back together and raced to respond.

"We could see debris in the surf break as we went down there, and could see it for about 300 metres before we caught up with where the choppers were. So you could clearly see they were searching the right spot. But most of that debris was sitting way out back outside the surf break," he said.

Mr Hardie says the surf was huge, and their's was the only boat that was able to make it out.

"We made it out, then spent about four and a half hours out there, searching among the debris. We went up to what was left of the boat and it was nothing bigger than maybe two metres long and half a metre wide. Most of it was in the water."

"We kept on searching until the light made it too dangerous."

He said they knew as soon as they got there, that those who'd come off the boat would be lucky to survive.

"I was amazed that three guys actually survived it. Absolutely amazed," he said. "We wear good wetsuits, have fins strapped to us, a proper lifejacket, water proof radio and all of that. And I thought to myself if we flip the boat, it's not going to be an easy job to get ashore. We had two choppers above us, and they had our backs."

He said it was among the hardest responses he's ever been involved with - because of the huge surf.

"Some of those sets were just huge. One of the sets that caught us must've been seven metres. Normally you can avoid the swell or escape it by heading parallel along the beach, and then going over it. But we got to the point where we couldn't go any further, and we had to beach the boat... which you never do if you can help it."

He says he'd been patrolling since 9am Saturday morning and everyone was just knackered. They didn't get out of there until midnight, and it was mostly body recovery as opposed to a rescue, which is really emotional.

"Last night was pretty emotional. This morning I went for a big walk on the beach with my dog to clear my head, and that helped. It's a good beach to clear your head, really good."

Patrols didn't get a boat in the water this morning to continue the search out back, because it was so treacherous. Brett Hardie says he's not surprised.

"It was marginal yesterday, but it's even bigger today. They'll only be able to do a shore search."