Any whirlpool that contains a downdraft – one capable of sucking objects beneath the water’s surface – is called a vortex. The lake having a whirlpool is highly unlikely, bordering on impossible but I’m not going that far. Whirlpools also form at the base of waterfalls and man-made structures such as dams. A short-lived whirlpool sucked in a portion of the 1300 acre (~530 hectares) Lake Peigneur in Louisiana, United States after a drilling mishap on 20 November 1980. The lake though (like many reservoirs in California) are mind shatteringly cold especially if you jump/fall in and end up below those first few feet of warm(ish) water near the surface. Whirlpools may form wherever water is flowing, from creeks and streams to rivers and seas.

This was not a naturally occurring whirlpool, but a disaster caused by underwater drillers breaking through the roof of a salt mine. The lake then drained into the mine until the mine filled and the water levels equalized, but the formerly-ten-foot deep … https://www.huffpost.com/entry/whirlpool-video-latvia-river_n_3147329 A whirlpool is a body of swirling water formed when two opposing currents meet.