"He was getting pretty cold and showing signs of hypothermia," Carson said.
Carson has been a member of Coastguard Wanganui for more than 13 years and has spent 480 hours in the past year training his fellow volunteers, and is also on-call as a duty skipper every two weeks.
He said training was important to the Coastguard's work.
"It's a matter of making sure we're safe and the best way to be safe is to know exactly what we're doing."
Whanganui was a boat-oriented place - with about 1000 boats registered with Coastguard - meaning it was a vital service for the region, Carson said.
"We do a lot of stuff in the background too."
Coastguard New Zealand chief executive Patrick Holmes said Carson had a great respect for volunteers.
"(And he) uses his wealth of knowledge and experience to help his unit reach their full potential, all while making sure they're looked after."
Never was this more evident than when he and his crew rescued a diver in a medical emergency.
"Mike is a team player who fosters a positive atmosphere by encouraging others, offering support, being generous with his time, and being actively involved in many aspects of his unit."