Lake Peigneur - The lake that ate Louisiana

From Damn Interesting:

On November 21, 1980 an oil drilling crew punctured the top of an underground salt dome of the Blue Diamond salt mine.

A giant whirlpool formed. It swallowed another nearby drilling platform whole, as well as a barge loading dock, 70 acres of soil from Jefferson Island, trucks, trees, structures, and a parking lot. The sucking force was so strong that it reversed the flow of a 12-mile-long canal which led out to the Gulf of Mexico, and dragged 11 barges from that canal into the swirling vortex, where they disappeared into the flooded mines below.

After three hours, the lake was drained of its 3.5 billion gallons of water. The water from the canal, now flowing in from the Gulf of Mexico, formed a 150-foot waterfall into the crater where the lake had been, filling it with salty ocean water.

Within two days, what had previously been an eleven-foot-deep freshwater body was replaced with a 1,300-foot-deep saltwater lake.