DENISON, Texas (AP) — Water draining into the spillway on a lake along the Texas-Oklahoma border has formed a whirlpool.

The whirlpool formed on Lake Texoma near the Denison Dam spillway after heavy rains raised the lake to flood level.

The U.S. Army Corps of Engineers Tulsa District manages the lake. Spokesman Brannen Parrish told The Dallas Morning News a vortex isn't unusual when the lake is releasing a lot of water, such as after recent floods. He said it's like the suction of a bathtub when it's draining water.

The vortex is 6 to 8 feet in diameter, big enough to swallow a boat. But Parrish says it's walled off with buoys to keep vessels from approaching.

The agency posted video of the whirlpool on its website three weeks ago, prompting attention.