"I've got some big open water swims planned overseas this year so I decided doing the double Taupō would be a good training swim."
It's the longest swim recorded by the teenager who has previously completed the crossings of Cook Strait, Foveaux Strait and one lap of Lake Taupō.
Caitlin, who swam Cook Strait at age 12, was raising money for the Westpac Rescue Helicopter after the Waiheke Island to Auckland event was cancelled due to Covid-19 restrictions.
"[The double crossing] was hard, it was challenging. We started at 1am on Saturday and finished at about 5am on Sunday.
"The middle of the swim was in the dark and I had to just follow the LED strip on the side of the IRB. That's probably one of the hardest things, trying to gain mental focus and just relax, not think about how far I had to go and remember why I was there and what I'm training for."
She says the rescue helicopter is a worthy cause and she wanted a replacement for the Waiheke to Auckland fundraising swim, which she has done three times as part of a team relay.
"I think it's a great cause to support and I'm really happy to support it."
She plans to head to Japan in July to swim the Tsugaru Strait, part of the Ocean's Seven Challenge, a marathon swimming challenge consisting of seven open water channel swims around the world.
"That's 28km. It's a good excuse to travel. I'm super lucky that there is so much water around for me to train in New Zealand."
When it comes to finding a coach, Caitlin has the perfect man in her corner in Phil Rush, the first person to ever swim the Lake Taupō double-crossing. He is also the world record holder for the fastest two and three-way swim of the English Channel.
"It was really helpful having him there, he knew what I was going through and he was really supportive," Caitlin says.
"He's been there since the beginning of my ultramarathon swimming career. He's guided me through lots of things."
Phil says Caitlin is a talented young swimmer with a bright future.
"For somebody of 17 years of age to be able to mentally and physically cope with pretty well swimming continuously for 28 hours - it was pretty fantastic," he says.
"She'd done a lot of training and she's strong but once again she's only 17. Youth does play a great part, they bounce back and they can put their bodies through a hell of a lot once they realise they can do it."
Phil was 20 when he completed the swim himself, in 1985, and says he did get a little emotional seeing Caitlin follow in his footsteps.
"I love swimming in freshwater, I don't like the sea that much and I think Caitlin's a little bit that way as well.
"The turning point and getting down to the finish, she mentally just beat it and it was good to see. I can offer her tips with her mind because I've been there and I think that was a real benefit."
He will travel overseas with Caitlin when she goes to compete and is confident she can make the most of every opportunity.
"She holds good speed, she's very determined and strong, and she can do anything she puts her mind to. The swims (overseas), compared to what we've done, I don't believe are too difficult."