The two trampers who went missing in bush north-west of Nelson say they spent nearly two weeks without food - and their only saving grace was water they had found.

An intensive search and rescue operation had been underway to find Dion Reynolds and Jessica O'Connor, who have been in Kahurangi National Park since May 8.

The pair were in a very rugged and remote part of the park when a search helicopter spotted smoke from a fire they had lit and rescued them yesterday, police said.

Dion Reynolds revealed that he had only realised the pair were walking in a loop around a Manuka forest after he recognised one of his own footprints in the mud.

"I told Jess we need to stop now because that's my footprint. We were very lost at that point," he told RNZ today.

Despite spending the night in a comfy bed in a long while, Reynolds said he "couldn't sleep a wink" last night because it was hard to process everything that had happened.

Reynolds said they had gone into the bush on May 8, rather than their planned May 9 date.

"We went up the river for two days and made our first campsite, and pretty much the first thing that started going wrong is we ended up burning our socks, I burnt three out of the four socks that I'd had after the river crossing."

The next day as they carried on they realised they had made more progress than they expected to, he said.

"We looked at our map and what we thought was the waterfall that we got to wasn't what we got to really. We decided to go up the hill and thought we'd cut across the track and carry on down towards the lake.

• 'Never lose faith': Missing trampers found alive after 18 days

"The next day once we camped up on that hill, the fog had come in and it really disorientated us.

"We thought we were going to just carry on heading east up the hill in the same direction that we were, but obviously it wasn't."

After they had passed through a forest, Reynolds told Jessica that they needed to stop because he realised they were going around in circles.

They decided to camp there and it was another couple of days of fog but they were running low on water, he said.

"We were on top of a hill, there was no fresh clean water. Jess had gone to this little rocky puddle that we ended up boiling the water out of, and that was all right for us.

"The next day we kept on going until we found this hilltop and the fog was still there."

Once the sun came out, they decided to get a sense of where they were to find fresh water, Reynolds said.

"We only had two days worth of food left and we were going down a gully, real steep, it turned from a small rocky stream into pretty serious waterfall.

"On our way down, I twisted and sprained my ankle... we got to a waterfall that was 15-20m high and we just looked at each other were like 'we can't go down that, we need to stop and go back up the hill and stop'."

Once again, they made camp and waited it out but Jessica had also injured her back after falling while trying to get water, Reynolds said.

They spent 13 days without food, but the "saving grace" was a stream of water that was two minutes away from the gully, he said.

"That's what kept us alive."

Jessica had contacted her family prior to the trip to assure them that they'd be definitely be back by her birthday. But as time passed, the pair relied on each other not to break down and made sure not to lose hope.

"It was a real surreal experience, trying to keep positive, trying to keep hopes up.

"Jess and I would wake up in the morning and think if it's not today, it's tomorrow, and if it's not tomorrow, it's the next day."

'I've never been so God damn happy in my life'

About a week ago, he said they spotted a helicopter flying over and lit the fire again to grab its attention.

"It got to about what I assumed would be five-thirty or six o'clock in the evening and we saw a Westpac Rescue helicopter fly up the gully and straight at us... and they just didn't spot us because it was real poor lighting. After that, it really bolstered our hopes a whole lot."

The rescuers finally managed to locate them and went down to them.

"I've never been so God damn happy in my life ... First chopper came over and saw us and Jess went over the quarry and started waving at it.

"Then the medic came down... At that point I knew we were saved."

When they were winched up, Reynolds said he saw where they were camped and it was not where they had thought they were.

About 10 minutes into the ride, he said they got the "best chocolate bars I've ever had in my life."

Reynolds' family celebrated his return with drinks and pizza in Nelson last night.

By RNZ