Most of us find a 16km run a challenge, and almost all of us would find a 16km swim a challenge.
So a 16km swim, in choppy conditions, in a lake, is a very big ask.
Georgia Bavington, 15, did just that yesterday morning when she swam the length of Lake Rotoiti.
The Pāpāmoa schoolgirl left Okere Falls at 6.45am and made it to Korokitewao Bay by 11.15am, meaning she swam at an average pace of more than 3.5km/h.
It was the second time Bavington had swum that distance in one hit, but Friday morning's effort was "just a training swim" in her lead up to swimming Cook Strait at the end of February, "depending on her place in the queue".
She was accompanied by her father and Rotoiti resident Craig Milbank in a boat, and Pāpāmoa surf lifesaver Liam Davoren, 15, paddled alongside her.
When Bavington got out of the water, the main thing on her mind was hunger.
She could stop and tread water during the swim to drink water and electrolytes and eat small snacks, but she couldn't lean on anything or touch anyone.
Bavington passed the 4.5 hours thinking about what she was going to eat afterwards and what she was going to do for the rest of the day.
She was pleased with her speed in the "annoying white caps".
"The conditions meant that I could only breathe one side for a while, so one shoulder is slightly more sore than the other. The first part was the hardest, it was like swimming in the ocean and the wind was right against me.
The water temperature was 22C, warmer than Bavington's last ocean swim.
When asked what her long-term goal was, she said: "possibly swimming the English Channel".
"Just completing other long swims around the world would be good."
Sheryl McLay from Shorebreak Aquatics has coached Bavington for the last two and a half years.
"It was a year and a half ago when she told me she wanted to do the Cook Strait, but I am guessing it had been in the back of her mind before that."
From point to point, Cook Strait swim is 20km, but most swimmers end up doing about 28km as they are pushed in a curve by currents and tides.
Bavington started swimming lessons at age 3 and hasn't stopped since.
McLay admits training for long distances "can be tedious" in the club's 25m pool.
Bavington has been swimming two times a day, most days, clocking up about 18km to 20km in the past few months.
"She has definitely got an aptitude for this sort of longer stuff. She doesn't get angry very often. Sometimes I have to remind myself she is just a 15-year-old kid."
Sonya Bavington, Georgia's mother, has told her daughter "if she ever wants to stop, she just needs to say so".
"Why would I want to do that?" was Georgia's response.