The last time Lorraine Moser visited the Onehunga War Memorial Pool, she almost died.

Now she has returned to thank the heroes who brought her back from the brink.

"I'm just so blessed that I was in the right spot and we had the right people that knew what they were doing and and didn't give up," she said.

"I really want to give them a heartfelt thank you, and encourage them to keep doing what they're doing."

On 19 May, Moser was halfway through her usual three kilometre swim when her heart gave out, and she started drowning in the middle of the pool.

"A really strange feeling, I just got this really strange feeling over my body and I thought 'oh gosh I better stand up.' But before I even had a chance to stand up, I was out," she recalled.

"I was told by numerous people in the pool that they just gave CPR for well over 15 to 20 minutes and they didn't stop and that's really what saved my life."

A fit and avid swimmer, she said the sudden cardiac arrest came as a complete shock.

But 19-year-old lifeguard Tash Corbin and 18-year-old Damon McKinstry wasted no time.

The pair took turns performing CPR until the ambulance arrived.

"I know for me my first instinct just kicked in and I just jumped in straight away to grab her," Damon McKinstry said.

Tash Corbin said the 15 minutes they spent doing CPR felt like hours.

"Every now and again she would give like little signs of life and, I mean, I was on the verge of tears nearly when I was doing it," she said.

"There's just no really thought going through your brain, you just got to keep going."

Despite being celebrated as heroes, the young lifeguards were staying humble.

"We do it in training, we've trained for it but I never actually thought I'd have to use it, so it is a pretty good feeling, I'm not gonna lie," Corbin said.

"Yeah it's a good feeling but it's just like another day at work," McKinstry added.

"Exactly, I mean it's part of the job."

But Moser's friends, who she swam with regularly, said Corbin and McKinstry deserved to be celebrated.

"I felt really quite helpless, but that was when the lifeguards got involved," fellow swimmer Tony Walker said.

Another swimmer, Russell Brown, said he was stunned by the lifeguards' composure.

"Not only did they know what to do but they just did it without fluster. You know, most people, even I was in a flap, and I was just so impressed with how composed the kids were."

Lorraine Moser said she was eager to join her crew in the water again.

But after spending five weeks in hospital, where her lungs were drained and she underwent open heart surgery, she planned to take it slow.

"Part of it's psychological, and not just for me, for people around me, that they feel safe when I'm back in the pool," she said.

"So I think I will get in the pool in stages, do a little bit of flutter board, and then yeah, absolutely want to get back in the pool."

Moser said it would be about six months before she was back in peak form, but her recovery was going swimmingly.