Cook Strait
Discovery
Abel Tasman was in the Cook Strait area from 18 until 26 December 1642. Although he showed the strait as a bight on his chart, he noted the tide was running from the south-east and therefore concluded that there might be a passage. He named it Zeehaens Bocht, after one of his ships. The true nature of the strait was discovered by Cook on 22 January 1770. While the Endeavour was undergoing repairs in Ship Cove, Cook, Banks, and Solander took the ship's pinnace to explore the head of what seemed to be a large inlet. After rowing 4 or 5 leagues without reaching their objective, the party landed on the south-east shore. Cook then climbed a hill and sighted the eastern sea, thus proving the strait's existence.
Name
The Maoris knew the strait as Raukawa. The origin and the meaning of the name are obscure.
The European name is, of course, after Captain Cook and it appears on the chart of 1770. It seems likely that the name for the strait was agreed upon by Cook only because he was pressed to do so by members of the Endeavour party, especially Joseph Banks.
The Sea Floor
Cook Strait is the stretch of water separating the North and South Islands of
New Zealand. It connects the South Pacific Ocean and the Tasman Sea through the
centre of the New Zealand land mass, and is 14 miles at its narrowest, between
Cape Terawhiti on the south-east coast of Wellington, and Wellington Head near
Tory Channel. Much of the shore of Cook Strait on both sides is composed of
steep cliffs.
The beaches of Cloudy Bay, Clifford Bay, and Palliser Bay are
composed of boulders with steep and high storm beaches. Although these bays
shoal gently down to 70 fathoms, where there is a more or less extensive
submarine plateau, the bottom topography of the strait is complex. The major
features of this bottom topography are, however, an eastern Cook Strait Canyon
with steep, and in some places, precipitous walls descending eastwards into the
bathyal depths of the Hikurangi Trench which lies off the east coast of the
North Island.
The upper part of the canyon divides into three arms: the South
Arm, lying near the centre of the strait with its head south-west of Wellington;
the Middle Arm with its head south of Tongue Point on the South Wellington
Coast; and the Wairarapa Arm with its head at the 20-fathom contour near the
western side of Palliser Bay. Centre Bank at a depth of 70 fathoms divides the
South and Middle Arms.
To the north-west of the Cook Strait Canyon, in the Cook
Strait Narrows, lies the Narrows Basin, where depths of water between 150 and
200 fathoms predominate.
Fisherman's Rock in the north end of the Narrows Basin
near the centre rises to within a few feet of low tide, and is marked by wave
break in rough weather.
Leading into the Narrows Basin from the north-west is
the North West Trough, a rather shallow submarine “valley” lying across the
northern end of the Marlborough Sounds. Its head lies near the centre line of
Tasman Bay. Near shore on both coasts from the Narrows both to north and west,
the bottom topography is most irregular, particularly around the coast of the
South Island where the presence of offshore islands, submerged rocks, and the
entrances to the sounds, create violent eddy conditions. Cases in point are
Koamaru Hole, 100 fathoms off the entrance to Queen Charlotte Sound; Jacksons
Hole, 150 fathoms off Cape Jackson; Chetwode Hole, 80 fathoms off Chetwode
Island; and Sentinel Rock and Stephens Hole, 150 fathoms off Stephens
Island.
Tides and Winds
Since the early years of European settlement, Cook Strait has been notorious for its treacherous currents and high winds, often of gale force. The tidal currents now generated in the strait reach a velocity of about 8 knots westwards and 4 knots eastwards, but are very erratic depending on conditions of wind and weather. The strait lies between 41 degrees and 41 degrees 40 minutes South Latitude in the westerly wind belt known as the Roaring Forties and wind velocities of up to 150 m.p.h. have been measured in the vicinity of Wellington. As Cook Strait is the only large gap in the chain of mountains extending north-eastwards for 900 miles from Puysegur Point to East Cape, it is thus a natural channel through which air streams approaching central New Zealand are diverted and accelerated to pass between the North and South Islands. This local acceleration of the surface winds is most pronounced when the air approaches from directions between west and north-west or between south and south-east. The map below illustrates the pattern of flow through the strait on an occasion when the general air-flow aloft was from the west.
When the general air-flow aloft is roughly parallel to the mountain chain (and south-westerly flows are relatively frequent), a slight shift in direction causes a complete reversal of the surface winds in Cook Strait. The southerly change which is usually very sudden and on occasion violent, often arrives as a “line squall”. Winds from the north-westerly quarter predominate, however, being about twice as frequent as those from the southerly quarter. Strong gales (60 m.p.h. or more) occur about Wellington and in the strait about 30 times per annum, on the average, with maximum frequency in the late spring.
Swimming of the Strait
It is quite possible that, before the coming of the European, the strait was swum by a Maori. Within European times it is recorded that a South Island Maori named Whakarua-tapu, of the Kai Tahu tribe, swam the strait in order to save his life. Apparently after Te Rauparaha had returned from his onslaught on Kaiapohia (Kaiapoi) in 1831, he attacked the people of Wairau, and among the captives whom he carried back to the North Island in his canoe was Whakarua-tapu. When near the coast of the North Island, Te Rauparaha ordered Whakaruatapu to kill his own daughter, a child about nine years old; instead, he flung his daughter into the sea. Te Rauparaha then tried to kill Whakarua-tapu with his hatchet but the latter dived overboard and set off for the shore. Fearing death from Te Rauparaha's people, he changed course and made for the South Island which, by swimming and floating, he eventually reached. It is alleged that he landed somewhere in the vicinity of Queen Charlotte Sound.
The first European to swim the strait was Barrie Devenport who on 20 November
1963 made the crossing in the time of 11 hours 13 minutes. This feat was
repeated by Keith Hancox on 7 February 1964 in the time of 9 hours 34
minutes.