It's a staple of the Kiwi summer to scorch your feet on a sandy beach, and we also know it's worse when the sand is black.
Except every year, dozens of beach-goers get seriously burnt and some end up in hospital.
The black sand of Piha Beach and its scorching temperatures - ouch!
If you take a dip, getting back to the sanctuary of your beach towel can be a mission.
"I thought I could walk it, then I thought I'd better run and get my jandals!" said Leki Fonaki.
Given what his name means in Tongan, he should have known better.
"His name's the black sand!" yelled his mate.
On Friday, the temperature crept so high that many got a tinge of a singe.
"Luckily I did bring shoes because I was thinking of going barefoot. But it's just scorching hot the sand," said one woman visiting the beach.
Even those who tried to outrun the black sand eventually gave up.
But it's no joke.
Last weekend alone Piha's sand got the better of several beach lovers.
"They treated four people at the Surf Club with burns to their feet and they actually had to refer one to Saint Johns. The first response team came out and took them, I think, to hospital," said Louis Curham, Surf Life Saving patrol captain at Piha.
The treatment is a 20-minute shower as soon as possible.
"The longer the better. Just running it, leaving it under cold running water is just awesome. It'll help cool the burn down. And then after that if it is serious, if it's still quite painful, we can wrap it in Gladwrap," Curham told Newshub.
The black sand is 83 percent magnetite, a type of iron oxide, but it also contains 8 percent titanium.
It holds far more heat than white sand.
"The latent heat within a black sand beach is incredible and people just underestimate that," said Gary Payinda, medical director at Surf Life Saving NZ.
"And by the time they realise it, they often think 'well I'll just push on through'. And by then, they've soaked up enough thermal injury to burn their feet, to blister their feet."
One of the traps is that you can head down to the beach in the morning and the sand is pretty cool.
But by the time you head back at lunchtime or even later the sand can get dangerously hot. In fact, temperatures at Piha have been brushing 80C.
That's when the Crocs come in handy.
But if you do get caught, there's a trick - shuffle your feet below the surface, or wrap them in a shirt or towel - although wearing shoes is better.
"Don't try to tough it out, because literally the temperatures are well high enough to denature the proteins in your skin and create blisters. Then you can lose the top surface of your skin," Payinda told Newshub.
If all else fails, you can always try asking a friendly surf lifesaver for a lift.
