Deep in Yellowstone National Park in the U.S. state of Wyoming, you’ll find a small lake that looks, in every way, wholly unremarkable. The small body of water, Isa Lake, looks more or less like just about every other temperate forest inland lake in the United States. It’s modest in size, has a pleasant backdrop of woodland scenery behind it, and is covered in lily pads with banks packed tight with plants–at first glance, there is truly nothing unusual about it.
If, however, you examine the drainage pattern of the lake, you find something pretty remarkable. By the pure chance of sitting directly upon the continental divide at an elevation of 8,262 feet, Isa Lake drains into creek and river systems on each side of the divide like water pouring down the peak of a roof. The river systems it drains into manages, over the course of thousands of miles, to flow all the way to the Gulf of Mexico and into the Atlantic Ocean and, simultaneously, down the opposite slope of the continental divide all the way to the Pacific Ocean.
Rain falling upon Isa Lake, then, has just as much chance to end up in the Pacific Ocean as it does in the Atlantic Ocean. Isa Lake is the only known example in the world of a naturally occurring bifurcated lake that drains into two separate oceans. The only other known example of a multi-ocean bifurcated lake is the man-made Gatun Lake, created during the construction of the Panama Canal.