Sea Whirlpools

Whirlpools (or maelstroms) are some of the most dramatic and photogenic behaviours of the sea: spinning columns, boiling “boils” and eddies that twist surface foam into rings.

They are not monsters from myth, but the result of predictable fluid dynamics: tides, currents, and the shape of the coastline and seafloor.

At a basic level, a strong whirlpool needs three things: a lot of water moving past a bottleneck, a sudden change in depth or underwater obstacle, and rapidly changing flow (usually tidal). Exactly the same thing that happens when you empty your bathtub after a nice bath with sea salt and essential oils.
When huge volumes of water are forced through a narrow strait or over an uneven seabed, the flow becomes turbulent. That turbulence and shear produce rotating currents that can line up into vortices visible at the surface. Where an opposing flow, underwater pinnacles or abrupt depth changes exist, standing eddies, “boils” and persistent vortices form; when tides reverse, they can re-energise and reshape the whirlpool every few hours.

Where to see them

• Saltstraumen, Norway — one of the strongest tidal currents on Earth; enormous volumes of water squeeze through a narrow strait, producing vortices and intense turbulence.
  
• Moskstraumen / Maelstrom, Norway (Lofoten area) — the classic “maelstrom” of legend; a system of tidal eddies between the Norwegian Sea and Vestfjorden formed by strong currents and complex bathymetry.
  
• Naruto whirlpools, Japan (Naruto Strait) — spectacular, regularly visible whirlpools caused by tidal exchanges between the Inland Sea and the Pacific; eddies can reach many metres across and are a major sightseeing attraction with boat and bridge viewpoints.
  
• Gulf of Corryvreckan, Scotland — a turbulent whirlpool in the strait between Jura and Scarba driven by tides, a deep sea hole and an underwater pinnacle; famous for violent surface boils and as a challenging spot for boats.
  
• Old Sow, Bay of Fundy (between New Brunswick, Canada and Maine, USA) — the largest tidal whirlpool in the Western Hemisphere; formed where powerful Bay of Fundy tides meet local bathymetry. Locally notorious and often called the “Sow.”
  
• Seymour Narrows / Discovery Passage, British Columbia (Canada) — a narrow passage with very strong tidal currents and frequent turbulence; historically dangerous to shipping (Ripple Rock) and still a site of strong eddies and boils.
  
• Strait of Messina, Italy (Scylla & Charybdis legend) — the geology and colliding currents create local whirlpools referenced in Greek myth; a historically famous example of a Mediterranean whirlpool area.
  
• Skookumchuck Narrows, British Columbia (Canada) — dramatic tidal rapids and standing waves that occur when huge tidal volumes rush through a constricted channel; smaller whirlpools and strong boils form at peak flow and draw kayakers and spectators.