NZDF Colonel Rian McKinstry says the recovery team went beyond limits in yesterday's mission.

Wading through boiling, knee-deep acidic sludge, the team of experienced specialist soldiers tasked with recovering six bodies from Whakaari/White Island looked at each other in doubt.

The battle-hardened veterans from the Defence Force's SAS E Sqaudron team had never found themselves in a situation like this before.

NZDF/SUPPLIED. Two figures make their way towards arduous conditions to recover six bodies. The defence force team had to stop and regroup part way through the mission to assess whether they could carry on.

Underneath three layers of special garments their bodies were drenched in sweat, gas masks fogging up, claustrophobic heat attacking their resolve. There was a six per cent chance of being eliminated in another eruption.

Matt, a member of the SAS whose identity cannot be revealed, was commanding the recovery mission on Friday at the unpredictable volcano.

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Of the 47 people who were on Whakaari when it erupted on Monday, eight had remained behind.

Growing pressure to retrieve the bodies had spurred the authorities into action, and a plan was made to go in at first light on Friday morning before they became entombed.

ROSA WOODS/STUFF Colonel Rian McKinstry from the NZDF recounts details of the mission to recover bodies from Whakaari/White Island.

Matt, and the rest of the eight person unit, were transported by helicopter from the HMNZS Wellington, stationed a short distance from the island.

About an hour and a half into the operation, fatigue had pushed the team to a crossroads.

They returned to the boat, poured water down their suits, and discussed what to do next.

"Our thoughts were we can't not do it.

"We were thinking, we don't have enough time to stop again, we'll find a way through this."

ROSA WOODS/STUFF NZDF Colonel Rian McKinstry shows us what the recovery team wore to stay safe during their White Island operation (This video was first published in December).

After adding two members to the team, they went back into the hostile territory and didn't stop again until the six bodies had been recovered.

The initial track from boat to island had been relatively easygoing: the ground underfoot was high and crusty, Matt said.

It was when they reached the bodies at the island's crater that they hit dense mud, and had difficulty lifting equipment over sharp ravines.

"It was unbelievable, not a condition we train for or ever expect to operate in, it's just so much hotter than you could expect."

NZDF/SUPPLIED The team, huddled in yellow suits, gather at the entrance to the island.

Underneath their yellow waterproof body suits was another two layers of clothing: a green, cotton undergarment used to soak up sweat and a black charcoal-lined suit to filter out gases.

A 15 kilogram breathing-set backpack contained melting ice and an oxygen mask could only supply air for four hours.

With their heavy apparatus, the team worked quickly in pairs to move the bodies to a central location, where a helicopter transported them to the HMNZS Wellington navy ship, a short distance from the island.

Once the team got back to the HMNZS boat themselves many of them were "pretty crook", Matt said.

"We are talking about people trying to re-hydrate at sea", Colonel Rian McKinstry said.

"There were a few people vomiting, drinking water, and everyone was very fatigued."

All recovery team members have since been medically checked and assessed as healthy, McKinstry said.

The team went to their depths to complete this mission, he said.

"These guys have gone past the limits of endurance, what's taken them past some of those limits has been their professionalism, but it's also their human nature - their understanding of the situation, and not wanting to not achieve this task."

Matt agreed, the enormity of the task had set in with them before they stepped foot through the island's thick ash.

"How we felt prior was just pressure, because everyone wants you to do this."

That everyone - the victims' families, the country, the world - was desperate for a successful mission and the team felt that deeply.

Relief still flows over Matt's face when asked about successfully recovering six people.

He was absolutely "stoked" to bring six victims' back to their families.

"There's been a sense of sadness too, for all the team, and that's been really hard, it's affected everyone."