"By the time we got out to him, there was one guy trying to help him but he was getting pulled under as well and so by the time we got there, my buddy Ryan dove for the first kid because his head was under water. I could tell that the first guy who got there had sucked up a lot of water and he was struggling to keep himself up too so I pulled him up and around by back and swum him to shore."
The man was airlifted to Middlemore Hospital by Auckland's Westpac Rescue Helicopter in a moderate condition and has since been discharged.
After dragging him to safety Mr Lynn rejoined Mr Aiono in the search for Mr Lemalu.
"We were there until the helicopters arrived, we just kept diving and feeling for this kid and just couldn't find him. As soon as you go down about 3 feet deep and it was just brown, just dark black water. It happened very fast."
Mr Lynn said he and Mr Aiono realised after around six minutes that hopes of finding the young man alive were very slim.
"After six minutes ... I looked at my friend and he looked at me and we didn't even have to say anything, we knew there was no possible way he was still alive. Honestly it didn't even really kick in until the helicopter had arrived and everyone was starting to get out of the water."
The duo, who had been in the country a matter of days before the incident, have been praised by police for their quick actions.
"Both [Mr Aiono and Mr Lynn] braved unfamiliar and extremely dangerous waters with no thought of themselves. There is no doubt they saved a life on Saturday and we thank you both."
Mr Lemalu's body was found just after 10am Sunday by members of the Wellington-based Police National Dive Squad.
Mr Lemalu is being remembered by his family as a young man who loved his family and friends - and above all, his faith.
Mr Lynn said he and Mr Aiono were mourning for the young man's family and the man who tried to save his life.
"We are just mourning for his entire family. It was something unfortunate that happened and it happened way too quick. I also feel bad for the first guy that was there because he was the one that had him, it is just unfortunate to be in that position too."
The pair plan to continue travelling New Zealand and visiting family over the coming month before returning to Utah.