(CNN)Wearing nothing but a bathing suit, a swimming cap and an underwater mask, the 40-year-old woman plunged into a carved-out section of a frozen Siberian lake, before diving under the ice to swim in water estimated to be around 32 degrees Fahrenheit.
Russian woman who swam under Siberia's ice may have broken the world record
Footage tweeted by the English language Siberian Times shows the 40-year-old woman from Moscow entering the carved-out section of a frozen Lake Baikal, before she started the underwater ice swim.
Yekaterina Nekrasova, who took up free diving four years ago, then held her breath for a minute and a half as she covered the 85 meters (279 feet) of a frozen Lake Baikal on January 7 -- the Russian Orthodox Christmas Day.
She is believed to have set a world record with her attempt. A spokeswoman for Guinness World Records told CNN they have received details of Nekrasova's attempt but have yet to verify the landmark swim.
Footage filmed from above the surface shows members of her support team following behind in wet suits, in case of emergency. According to the Siberian Times, holes were cut in the 10-inch-thick ice at regular intervals in case she needed to abort the swim.
The challenge was filmed from both above and beneath the surface. Nekrasova can be seen desce