Old Sow whirlpool

Old Sow is the largest tidal whirlpool in the Western Hemisphere, located off the southwestern shore of Deer Island, New Brunswick, Canada, and off the northeast shore of Moose Island, the principal island of Eastport, Maine.

According to mythical etymology the name "Old Sow" is derived from "pig-like" noises the whirlpool makes when churning; however, a more likely origin is the word "sough" (pronounced "suff"), defined as a "drain", or a "sucking sound". Early settlers to the area may easily have mispronounced "sough", as "sow" (rhyming with "cow") due to its similar spelling to other words with "sow-sound" endings, such as "plough".

The whirlpool is caused by local bathymetry and extreme tidal range where waters exchange between Passamaquoddy Bay and the Bay of Fundy, combined with the unusual topography of the location's sea floor at the confluence of the numerous local currents.

The whirlpools form in an area with a diameter of approximately 250 feet/75 metres, as determined by the president of the Old Sow Whirlpool Survivors' Association in 1997 by way of an aerial photograph. The photograph was calibrated using the Deer Island Point Light beacon tower of known width that was included in the photograph.