The largest tidal whirlpool in the Western Hemisphere forms in the waters between Eastport and Deer Island, New Brunswick, driven by the enormous tidal volumes funneling through the passage. Old Sow — named for the grunting sounds it reportedly makes — can reach 75 metres across at peak flow and is visible from the shores of Eastport, particularly from the Dog Island area. The best viewing is around the time of maximum tidal current, roughly two to three hours before high tide. The surrounding smaller whirlpools are called "piglets" by locals.