In Maori legend, the navigator Kupe discovered the strait while chasing a monstrous octopus called Te Wheke-a-Muturangi, pursuing it by canoe until he destroyed the creature in Tory Channel. When Abel Tasman arrived in 1642, he looked at the strait and saw a dead end -- a bight closed to the east, which he named Zeehaen's Bight after one of his ships. It took James Cook, arriving in 1769, to establish that the passage was navigable. He sailed through in 1770, and the strait has carried his name ever since. Whalers followed in the early nineteenth century, establishing stations in the Marlborough Sounds and along the Kapiti coast, drawn by the humpback and right whales that used the strait as a migration corridor.

Between 1888 and 1912, a Risso's dolphin named Pelorus Jack became one of the most famous animals in the Southern Hemisphere. Jack would appear in Admiralty Bay, near French Pass, and swim alongside ships travelling between Wellington and Nelson, guiding them through the treacherous channel. When someone attempted to shoot him from the deck of the SS Penguin, public outrage led to a 1904 law making Pelorus Jack the first individual marine animal protected by legislation in New Zealand. The dolphin continued his escort duties for another eight years before disappearing in 1912. No one knows what happened to him, but the ships that followed sailed a lonelier passage.

The strait's toll is long. In 1851, the barque Maria wrecked on rocks at Cape Terawhiti, killing 28. The paddle steamer City of Dunedin went down in 1865, taking between 50 and 60 lives. The SS Penguin struck Thoms Rock in 1909, killing 75 -- New Zealand's worst maritime disaster of the twentieth century. In 1968, the interisland ferry Wahine sank in Wellington Harbour during a ferocious storm. Even modern vessels are humbled here: in 2006, 14-metre waves caused the Interislander ferry Aratere to heel to 50 degrees, toppling rail wagons and injuring passengers during a seven-hour ordeal. Maritime New Zealand's expert witness later testified that had the ferry capsized, most aboard would have been trapped inside with no time to reach lifejackets.

According to Maori oral tradition, the first woman to swim Cook Strait was Hine Poupou, aided by a dolphin. In modern times, Barrie Devenport completed the crossing in 1962, and Philip Rush has done it eight times, including two double crossings. The youngest swimmer was 11-year-old Aditya Raut. Oceanographer Ron Heath once published a scientific analysis of the strait's currents using nothing but the erratic tracks of swimmers -- a creative solution from an era when measuring ocean currents was technologically difficult. Beneath the waves, submarine HVDC power cables installed in 1964 and upgraded in 1991 carry up to 1,200 megawatts of electricity between the islands. Proposals for a bridge or tunnel surface periodically, but the estimated cost equals 20 years of New Zealand's transport infrastructure budget, and the strait's seismic activity makes the engineering virtually impossible.

Eighteen thousand years ago, during the Last Glacial Maximum, the strait did not exist. Sea levels were 100 metres lower, and a vast coastal plain connected the North and South Islands. As the ice melted and the sea rose, the land bridge drowned. Today, the strait is a meeting point of the Tasman Sea and the South Pacific Ocean, a corridor for humpback whales counted annually by the Department of Conservation with help from former whalers, and a habitat for bottlenose dolphins, dusky dolphins, killer whales, and the endemic Hector's dolphin. Giant squid have washed ashore here. Fur seals haul out at Pariwhero, on the Wellington coast. From the air, the strait looks deceptively calm -- a band of blue between green headlands. The turbulence lies below the surface, where submarine ridges churn currents that rival the Straits of Gibraltar.