They call it the International Ice Swimmers Association and it makes the Polar Bear Club seem like a trip to the spa.

In this truly heart stopping contest, competitors must swim a kilometer in icy cold water with only goggles and a Speedo. It sounds so simple, but what goes into the contest and what swimmers face upon completing this challenge will make you shiver.

“Everyone says that I am mad and they ask me what drives me to the ice. And what amazes me is how many people follow,” said Ram Barkai, founder of the ISA, which last year held 13 National Championships.

Barkai spoke with Great Big Story, a project of The Weather Channel during a recent competition in South Africa. Admittedly an ice swimming challenge in Africa is a bit absurd, but so is the contest. High in the Lesotho mountains 15 people drove their bodies to near hypothermia.

“It’s a massive mental challenge to get in that water and keep going. It takes a lot of mind power, and that’s what I love. I love pushing the boundaries in these conditions,” said competitor Ryan Stramrood.

The average swim takes 15 to 20 minutes, just short of the amount of time doctors would get worried. Any longer and the body could go into hypothermic shock.

“You need around 20 percent body fat and need to be fit and to train your body and mind to know how to deal with the shock,” Barkai said. “Panic is the number one killer.”

Barkai describes the swim as literally trying to stay alive. Upon entering the 39 degree water that’s accessed from a giant hole they carve on a frozen lake, your body goes into extreme shock. It takes experience and stamina to will your body to breath.

After the first few minutes the body goes numb. Competitors must remind themselves to breath as the chill literally takes your breath away.

The beginnings of hypothermia wrecks havoc on the body as oxygen levels to the brain and blood levels are depleted. Toward the end, the nervous system starts to malfunction resulting in dizziness and possible amnesia.

As they come out of the water the battle has just begun. The brain starts to release blood from the core during a process competitors fondly call the after-drop.

In 10 minutes core body temperature can drop almost 10 degrees, sending alarms throughout your system. This is the scariest point for everyone. Then as they come out of it, they get what Barkai calls the “devil’s look,” a massive sort of tunnel vision as your only thought is to just hang on.

Sound like fun? When it’s all over they say it makes you feel like a champion. See the action in the video below.