Cook strait It's 26 kilometres of cold, rough water swimming against strong tidal flows and abundant marine life. Due to the underlying mountainous geography, the water can be extremely unpredictable with swirling eddies and upward currents. There are very few opportunities, in any given year, to attempt this swim.

Yes, you can swim the Cook Strait—the body of water separating the North and South Islands of New Zealand—but it is considered one of the most challenging and dangerous open-water swims in the world. The straight-line distance is approximately 22 kilometers (13.7 miles), but the swim is notorious for its extremely powerful and unpredictable tidal currents, which can pull swimmers far off course, often requiring them to cover much more distance. The water temperature is another major hurdle, typically ranging from a chilly 14°C to 18°C (57°F to 64°F), necessitating high cold-water tolerance. Furthermore, the strait is home to significant marine life, including sharks and jellyfish. Because of these hazards, the "Cook Strait Swim" is strictly regulated and requires a support boat, a qualified navigator, and an official observer to verify the attempt. As of 2026, fewer than 150 people have successfully completed the solo crossing, making it a "Holy Grail" for marathon swimmers alongside the English Channel and the Molokai Channel.