Just off the coast of Eastport, Maine, in the tidal waters of Passamaquoddy Bay is a swirling, gurgling natural vortex of water known as a whirlpool. The Old Sow whirlpool is the largest whirlpool in the western hemisphere and the second largest in the world.

The "self-appointed President for Life of the Old Sow Whirlpool Survivors' Association" wrote in an August 2001 article for Smithsonian Magazine, "[Old Sow] is reluctant to disclose her mysteries from a distance. She'd rather catch the naive or careless unawares, and from up close, in a boat...in the 'sty.'"

Old Sow got her name because of the distinctive pig-like noises it makes as the water swirls together. The massive whirlpool, sized at about 250-feet wide, is caused when the current flows into the Western Passage, crosses a deep trench, flows over a deep sea mountain, and meets a few counter-currents.

Although science fiction has given us the image of a deep, swirling hole of water reaching to the ocean floor, Old Sow doesn't always look like that. According to the Old Sow Whirlpool website, "A rare major funnel is more apt to appear when tides are running especially high (as during spring tide), coinciding with strong winds."

Old Sow presents danger to smaller boats and those unprepared for it's pull, but the National Oceanic and Atmospheric Administration says they're actually great for the ocean environment. "It causes nutrients and tiny sea creatures normally found in the bay’s colder, deeper waters to rise to the surface. This process, called upwelling, ensures good eating for the resident fish and seabirds."