A girl who swam the length of Lake Taupō in 13 hours says swimming pools' lane ropes bother her.

"I feel more free in the open water than I do in the pool," Caitlin​ O'Reilly​ said.

"In Lake Taupō, there are no limits."

The 14-year-old Aucklander is the youngest female to swim the lake's 40.2 km length - a distance longer than the English Channel [33.8 km].

Caitlin left the lake's southern end at Waihi at 4am on Thursday.

"Leaving the shore was the hardest part.  But I figured out why I was doing it in my head.

"Then I just put my dead down and got on with it."

As per International Marathon Swimming rules, Caitlin did not wear a wetsuit and was not allowed to rest on her support boat.

Her support crew, which included marathon swimmer Philip Rush, passed her food and liquids.

"I drank Gatorade and ate dinosaur lollies," Caitlin said.

"It was cold for the first couple of hours before dawn, but once the sun came out the water was really warm.

"I go through songs in my head [while swimming] and I think about all sorts of things. Sometimes I think about nothing and just focus on my stroke."

Caitlin reached the Taupō Yacht Club at the lake's northern end after 13 hours and 26 minutes.

"I'm proud of myself and I'm happy I completed it. But I'm so sore, and tired," she said.

Caitlin is no stranger to long swims. In 2017, aged 12, she swam across the Cook Strait.  The 26-km journey took her 7 hours and 19 minutes and made her the youngest female and youngest New Zealander to complete it.

"I have been training twice a day for 1.5 hours, five or six days week [for the Lake Taupō swim]," Coast Swim Club member said.

"Some weekends I'd do a 10 km swim with friends, or stay at the pool longer, depending on the weather."

The Carmel College student said she planned to complete the Ocean 7, having already knocked the Cook Strait off. 

The marathon swimming challenge consists of the following seven open water channel swims:  the North Channel between Scotland and Ireland, the Cook Strait, the Molokai Channel in Hawaii, the English Channel, the Catalina Channel in California, the Tsugaru Strait in Japan and the Strait of Gibraltar between Spain and the African continent.

Caitlin plans to cross the English Channel next summer, but will be racing in the pool in the meantime.

"We've got Auckland regionals and nationals coming," she said.

"In the pool, I swim butterfly and long-distance freestyle, 800m and 1500m.  I'm training hard for that."

The youngest person to swim Lake Taupō's length is Kaine Thompson, who swam it when he was 14 years and a month old, in 1990. Thompson gave up swimming a year after the record swim.

Source: Stuff.co.nz