The Grand River Dam Authority police say a 16-year-old boy suffered a spinal injury after jumping off a 50-foot high bluff at Grand Lake.
It happened just after noon on Saturday in the "Three Fingers" area of the lake.
His family was able to render aid and get him out of the water until emergency responders arrived, GRDA says.
Officers say it is not clear if he was injured on impact or if he hit something under the water.
The boy has been flown to a Tulsa hospital.