To most, this is not the time of year to be tempted outdoors for a swim. In Rauhaniemi, however—a beach in Tampere, Southern Finland—taking a dip in sub-zero temperatures seems to be the perfect way to beckon in the New Year. ‘Avanto’ is Finnish for ‘hole in the ice’, and during the winter months spots like Rauhaniemi (there are over 260 registered in the country) are descended upon by brave swimmers, ready to face the cold and plunge into the freezing water. It was during a trip back to Tampere from the sunny climate of his adopted-home of California that Finnish photographer Markku Lahdesmaki encountered the group of lionhearted swimmers that feature in his project Avanto.

“Taking a plunge in an ice cold lake is a common ritual in Finland, so much so that there is a word for it: Avanto,” Lahdesmaki says. “Of course, Avanto also involves another Finnish staple, and the sauna and the smoke from the chimney told me that at least the swimmers would have the warmth of the sauna after their time in the lake.” A tradition that stretches back to at least the 17th century, the outdoor exercise involves darting between the extreme, cleansing heat of a sauna and its polar opposite: the refreshing shock of icy water. Ice swimming is said to hold great health benefits including pain relief, stress alleviation and paradoxically, cold prevention, by bolstering your immune system.

Not immediately convinced on arrival, Lahdesmaki arrived with his camera wrapped up like an explorer, in defence of the -11 degrees Fahrenheit weather. But after pondering how best to capture the surreal atmosphere of this winter entertainment, the photographer decided to leave the sidelines, strip off and join his countrymen in the icy water. “How could I make them comfortable with me capturing them in the midst of this past time? And then it hit me…I need to join them. So, I promised them that I would do the polar plunge myself after I photographed them. And that is exactly what I did.”