Cottle said the area the trampers were lost in was "one of the harshest" in New Zealand.
"It's insanely rugged. It's insanely remote as well, hence we had to use helicopters to drop teams into their start positions, otherwise it would take us a day or so to even get to where we want to search," he said.
In his first search stint he spent two days in there before coming out, and said he had to do more than 100 river crossings in that time.
"It's not a place that people go often. There are areas in there that are even a no-go zone for locals."
Cottle said there were a lot of things that created danger for trampers in the area.
"It's steep, rugged. In this climate it's always slippery. Yeah, it's just harsh, very harsh - but beautiful. That's the problem. Dangerously beautiful."
Cottle was at the base when the helicopter unit came back to tell them they had found the trampers.
"The energy just flew through the roof. There was a lot of hurrahs and bits and pieces.
"I was able to be with [O'Connor's] parents when we told them they were picked up alive and well. It's the best feeling I have ever had in search and rescue. It's what we do it for."
Cottle said O'Connor's father began to tear up, which in turn made him become tearful as well.
"It was just emotional joy and just relief flooded back through us."
He said searchers still knew there was a high probability the trampers were alive, because they knew they had gone in there with the correct gear, and that O'Connor had good background knowledge and survival skills.
"We're trained to know their survival probability was still pretty high ... that's why we were still going so hard.
"They knew a bit about what to do, staying put and being by a water source ... It's the gear that pulled them through, really."
By the time they were rescued, O'Connor and Reynolds had gone 13 days without food, and had suffered minor injuries.
Reynolds told RNZ they became lost after fog settled in and disoriented them.
He had only realised they were walking in a loop around a Manuka forest after he recognised one of his own footprints in the mud.
"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."
Seeing a rescue helicopter flying in the area bolstered their spirits, and the pair were overjoyed when they were finally spotted.
"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."
Cottle said the Golden Bay community were also to thank for the rescue.
"It's actually been this little tiny Golden Bay community that's helped bring them home, in the sense of hot food drops, baking. Everything about this community just helped in any way they possibly could."
Some rescuers were still being flown out of the bush today, as they had to spend the night until they could be safely winched out.
- Additional reporting by RNZ
