Just before 4:30 pm on Saturday, Madera County deputies responded to Blue Jay Point after a woman was brought to shore.
Officials say 81-year-old Claudia Libenson was swimming with her husband when she became fatigued.
Liberson started having trouble breathing and lost consciousness.
Witnesses say water went over her head while rescue attempts were made.
Good Samaritans performed life-saving measures before first responders arrived.
She died at the scene.
Authorities have not released an official cause of death.