Cook Strait lies between the North and South Islands of New Zealand. It connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast, and runs next to the capital city, Wellington. It is 25 kilometres wide at its narrowest point, and is considered one of the most dangerous and unpredictable waters in the world.
The strait is named after James Cook, the first European commander to sail through it, in 1770. In Māori it has the name Raukawa or Raukawa Moana. Raukawa may mean "bitter leaves".
In Māori legend, Cook Strait was discovered by Kupe the navigator. Kupe followed in his canoe a monstrous octopus called Te Wheke-a-Muturangi across Cook Strait and destroyed it in Tory Channel or at Pātea.
When Dutch explorer Abel Tasman first saw New Zealand in 1642, he thought Cook Strait was a bight closed to the east. He named it Zeehaen's Bight, after the Zeehaen, one of the two ships in his expedition. In 1769 James Cook established that it was a strait, which formed a navigable waterway.
Cook Strait attracted European settlers in the early 19th century. Because of its use as a whale migration route, whalers established bases in the Marlborough Sounds and in the Kapiti area. From the late 1820s until the mid-1960s Arapaoa Island was a base for whaling in the Sounds. Perano Head on the east coast of the island was the principal whaling station for the area. The houses built by the Perano family are now operated as tourist accommodation.
During the 1820s Te Rauparaha led a Māori migration to, and the conquest and settlement of, the Cook Strait region.
From 1840 more permanent settlements sprang up, first at Wellington, then at Nelson and at Whanganui (Petre). At this period the settlers saw Cook Strait in a broader sense than today's ferry-oriented New Zealanders: for them the strait stretched from Taranaki to Cape Campbell, so these early towns all clustered around "Cook Straitas the central feature and central waterway of the new colony.
Between 1888 and 1912 a Risso's dolphin named Pelorus Jack became famous for meeting and escorting ships around the Cook Strait. Pelorus Jack was usually spotted in Admiralty Bay between Cape Francis and Collinet Point, near French Pass, a channel used by ships travelling between Wellington and Nelson. Pelorus Jack is also remembered after he was the subject of a failed assassination attempt. He was later protected by a 1904 New Zealand law.
At times when New Zealand feared invasion, various coastal fortifications were constructed to defend Cook Strait. During the Second World War, two 9.2 inch (23 cm) gun installations were constructed on Wrights Hill behind Wellington. These gun could range 18 miles (29 km) across Cook Strait.
In addition thirteen 6-inch (15 cm) gun installations were constructed around Wellington, along the Makara coast, and at entrances to the Marlborough Sounds. The remains of most of these fortifications can still be seen. The Pencarrow Head Lighthouse was the first permanent lighthouse built in New Zealand. Its first keeper, Mary Jane Bennett, was the only female lighthouse keeper in New Zealand's history. The light was decommissioned in 1935 when it was replaced by the Baring Head Lighthouse.
A number of ships have been wrecked with significant loss of life, such as the Maria in 1851, the City of Dunedin in 1865, the St Vincent in 1869, the Lastingham in 1884,SS Penguin in 1909 and TEV Wahine in 1968.
The strait runs in a general NW-SE direction, with the South Island on the west side and North Island on the east. At its narrowest point, 22 kilometres (14 mi) separate Cape Terawhiti in the North Island from Perano Head on Arapaoa Island in the Marlborough Sounds.]Perano Head is actually further north than Cape Terawhiti. In good weather one can see clearly across the strait.
The west (South Island) coast runs 30 kilometres (19 mi) along Cloudy Bay and past the islands and entrances to the Marlborough Sounds. The east (North Island) coast runs 40 kilometres (25 mi) along Palliser Bay, crosses the entrance to Wellington harbour, past some Wellington suburbs and continues another 15 kilometres (9.3 mi) to Makara beach.
The Brothers is a group of tiny islands in Cook Strait off the east coast of Arapaoa Island. North Brother island in this small chain is a sanctuary for the rare Brothers Island tuatara, while the largest of the islands is the site of the Brothers Island Lighthouse.
The shores of Cook Strait on both sides are mostly composed of steep cliffs. The beaches of Cloudy Bay, Clifford Bay, and Palliser Bay shoal gently down to 140 metres (460 ft), where there is a more or less extensive submarine plateau. The rest of the bottom topography is complex. To the east is the Cook Strait Canyon with steep walls descending eastwards into the bathyal depths of the Hikurangi Trench. To the north-west lies the Narrows Basin, where water is 300 and 400 metres (980 and 1,310 ft) deep.
Fisherman's Rock in the north end of the Narrows Basin rises to within a few metres of low tide, and is marked by waves breaking in rough weather. A relatively shallow submarine valley lies across the northern end of the Marlborough Sounds. The bottom topography is particularly irregular around the coast of the South Island where the presence of islands, underwater rocks, and the entrances to the sounds, create violent eddies.The strait has an average depth of 128 metres (420 ft).
The South and North Islands were joined during the last ice age.
The waters of Cook Strait are dominated by strong tidal flows. The tidal flow through Cook Strait is unusual in that the tidal elevation at the ends of the strait are almost exactly out of phase with one another, so high water on one side meets low water on the other. Strong currents result, with almost zero tidal height change in the centre of the strait. Although the tidal surge should flow in one direction for six hours and then the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions the reverse surge can be negated, and the flow can remain in the same direction through three surge periods and longer. This is indicated on marine charts for the region. Furthermore, the submarine ridges running off from the coast complicate the ocean flow and turbulence.
There are numerous computer models of the tidal flow through Cook Strait. While the tidal components are readily realizable, the residual flow is more difficult to model.
Cook Strait is an important habitat for many cetacean species. Several dolphins (bottlenose, common, dusky) frequent the area along with killer whales and the endemic Hector's dolphins. Long-finned pilot whales often strand en masse at Golden Bay. The famous Pelorus Jack was a Risso's dolphin being observed escorting the ships between 1888 and 1912, though this species is not a common visitor to the New Zealand's waters. Large migratory whales attracted many whalers to the area in the winter. Currently, an annual survey of counting humpback whales is taken by Department of Conservation and former whalers help DOC to spot animals by using several vantage points along the strait such as on Stephens Island. Other occasional visitors include southern right whales, blue whales, sei whales and sperm whales. Giant squid specimens have been washed ashore around Cook Strait or found in the stomachs of sperm whales off Kaikoura.
A colony of male fur seals has long been established near Red Rocks on the south Wellington coast. Cook Strait offers good game fishing. Albacore tuna can be caught from January to May. Broadbill swordfish, bluenose, mako sharks and the occasional marlin and white shark can also be caught.