The driver safely escaped her Jeep Cherokee uninjured before it sank, officials said.
Hall County Fire Chief David Kimbrell said the accident occurred about 8:15 a.m. at Clarks Bridge Road just before the bridge near the Olympic rowing venue.
The driver was southbound when she lost control, went over a guardrail and plunged into the lake.
The Georgia State Patrol is investigating the wreck. A specially equipped wrecker with a boom was called in to pull the car from the lake.