Environmentalist reflects on 'dark places' after marathon swim

The numbers speak for themselves — 33 hours in the water, 99km covered and one exceptional record to his name.

Jono Ridler is recovering from the longest unassisted open water swim ever in New Zealand but told 1News from hospital today he was in good spirits.

"Feeling a little battered and bruised as you can imagine," he told 1News.

"Slightly dazed but on the whole, I'd give myself a solid five or six out of 10."

Ridler arrived at Campbell's Bay just after 7pm last night having set off from Great Barrier Island at 10am on Tuesday.

His official distance is yet to be confirmed — and it could take months — but what is firmly established is the mammoth effort he's put his body and mind through.

"I went to some pretty dark places, I spent a lot of time just counting in my head to get through the hours," he said.

"I was coming up with poems in my head as well — you have a lot of time!"

A lot of time was spent battling rough conditions as well, with the environmentalist at some points experiencing 25 knots of wind and heavy, 2m swells.

"The biggest [challenge] really came last night when we were coming in and there's these big waves, swell, wind and my body just, I was still there mentally and really wanted to give it a good go, but my body just didn't have it and my legs were cramping up, my arms were in a bad state and obviously sleep deprivation and I was just starting to have hallucinations."

Such a story begs the question — why did he do it?

For Ridler, it's not about accolades — it's awareness around the state of the ocean, and in this instance, the health of the Hauraki Gulf.

Ridler, who has previously completed the "triple crown" of New Zealand endurance swimming with campaigns in the Cook Strait, Foveaux Strait and Lake Taupō, teamed up with Peter Burling and Blair Tuke's Live Ocean charity for his most recent endeavour.

Ridler said the swim emphasised his concerns.

"There wasn't a lot of marine life that I saw, literally 33 hours and I didn't see anything," he said.

"It's a single experience, but it drove it home for me."

Ridler was discharged shortly after his interview with 1News and already had plans for tomorrow — unbelievably, work.