More than a decade later, the Mount Maunganui man was preparing to take on the Chopper Swim Challenge to raise funds for two rescue helicopters; the Auckland Rescue Helicopter Trust and the Trustpower TECT Rescue Helicopter.
It was his way of paying back the team that saved his life all those years ago.
"The medics didn't give up on me so I won't be giving up on them," Marsden said.
The 57-year-old was no stranger to the water after spending most of his life interacting with the ocean through water sports and swimming.
He completed the Lake Taupo Epic 10 km swim this month where he came first in his 50-plus age group and placed third overall.
"I felt really great after the swim in Taupo, like I could have done it again," Marsden laughed.
Which is exactly the length of the 20 km swim that he would be taking part in on March 26 from Waiheke Island to Auckland City.
"I just thought it was a great way of combining my love of swimming and fundraising for the rescue helicopters," he said.
Marsden has been training about five days a week in preparation for the massive swim and said he had a lot of support from his family and local club, the Seamen Ocean Swim Squad.
"This is all about paying back the people who saved my life," Marsden said. "Anybody could need the rescue helicopter at any time."
Click here to donate to Nigel Marsden's fundraising page.
-Will be held on March 26 -Around 100 swimmers will swim in teams or as individuals -The swim starts at Waiheke Island and finishes at Auckland City -This is the third year the event has been held -More than $82,000 has been raised from the past two events