Strongest natural whirlpool
Maelstrom of Saltstraumen
40 kilometre(s) per hour
Noruega ()

Whirlpools are caused when strong tidal currents flow through narrow gaps between dry shores, or over shallows with deep water either side. The strongest tidal current in the world also produces the strongest whirlpool (or maelstrom). At Norway's Maelstrom of Saltstraumen, the tide runs at 25 mph (40 kph) and more than 105,668 gallons (480,376 litres) of water pass through the narrow strait that connects Skjerstadfjord and Saltenfjord over a period of six hours. Every six hours, the tide reverses and rushes either in or out of the straits. At peak flow, the tidal race produces a whirlpool typically 10 m (33 ft) wide and 5 m (16 ft) deep.