I was looking up Isa Lake in Yellowstone for some reason, it's a small pond that drains into the Pacific and the Atlantic/Gulf. The NPS website said it drains out the east to the Pacific and out the west to the Gulf so I helpfully said "eh, you got that backwards, right?" and they agreed and changed the website. Oops.
 

acknowledged to be the only natural lake in the world that drains to two oceans, but it also unique in that it does so backwards. Throughout the year, the western end of the lake flows into the Firehole River, which meanders east to the Missouri and Mississippi Rivers and eventually to the Gulf of Mexico. In spring, the eastern end runs into nearby Shoshone Lake, which then drains, via a very convoluted path, into the Lewis, Snake, and Columbia Rivers on the way west to the Pacific.

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