In the middle of a frozen lake in Banff, Alberta, a group gathers on the ice. The buzz of chainsaws and voices fills the air as they prepare for their descent.

Up on the surface, the wind blows and the sun shines, adding a bit of warmth to the frigid winter air. Below, the divers are wrapped in the cold embrace of the water, listening to the muffled footsteps from above as they traverse underwater.

They call themselves “freezedivers”—adventurers who brave sub-zero temperatures to explore a hidden world beneath the ice.