The Missouri State Highway Patrol says Linglong Li, of Carthage, was swimming and snorkeling with family and friends when she went under and never resurfaced.
It happened around 5:30 p.m. Tuesday near the Viola Marina.
On Monday, a 19-year-old man drowned while swimming in Pomme de Terre Lake at Hermitage State Park.
Troopers say Johntario Jones, of Wheatland, was swimming when he started having difficulties and went under.
Four people have drowned at Missouri lakes in the past week.