Winter Swimming, Krasnoyarsk, Siberia

Ice swimmers typically dip their heads below the surface to ensure that they are completely wet, whether or not the water is over their heads. They usually do not swim beneath the ice, as it is easy to get disoriented when turning around and not be able to find one's way back to the hole. Some ice swimmers avoid this problem by swimming from one hole to another, or by swimming under the ice while tethered to the shore. Due to the diving reflex, a swimmer is able to hold his or her breath for a long time while under the ice.
Maintaining the hole in the ice
One way that the hole is maintained at regular ice swimming places is with a pump that forces the water to circulate under the hole, preventing ice from forming. Small ice-holes can also be kept open by keeping a lid over the hole to prevent ice forming.