Beresnyeva made her debut at the 2000 Olympic Games, at the age of 15. After representing Ukraine at the 2004 Olympic Games, Beresnyeva migrated to Israel. After failing to qualify for the 2008 Beijing Olympics Beresnyeva returned to Ukraine. Originally a 800 meter freestyle swimmer she became a long-distance swimmer in 2008. Beresnyeva won the 25K open water race at the 2010 European Championships at her first ever race at that distance.
2011 FINA World Championships
Olga placed 15th (2:02:25.1) in the 2011 FINA World Championships in the 10K in Shanghai, China.