Tory Channel also known as Kura Te Au separates Arapaoa Island from Te Waipounamu.
Tidal streams of up to seven knots flow through the entrance to and from Cook Strait. These tidal streams cause a great deal of turbulence, which can be very dangerous.
In N sector winds the Tory Channel entrance usually poses little problem. However, S sector winds generally create a heavy ground swell and this swell, meeting the shore line, piles up creating a steep sea.
If combined with a strong outgoing tide, a series of dangerous breaking seas occur just outside the entrance. Passage through the entrance is undesirable in such conditions, especially in undecked boats, as they can be easily swamped.
Low-powered vessels trying to enter from Cook Strait against the outgoing tides will find least current close to West Head as far as Taranaki Rock. From there, the boat should be headed for Okukari Bay and allow itself to be swept over close to the northern shore. A counter-current forms along this area, as far around as Whekenui Bay.
If leaving Tory Channel against an incoming tide, least current is usually experienced close to West Head. During the incoming tide the current tends to sweep across the outer part of the entrance to the east and can carry boats on the dangers out from East Head.
There are several dangerous rocks in this area. Taranaki Rock on the West Head side dries at Spring Low Water and should be given a wide berth as the strong tide can easily sweep a boat on to the rock. There are rocks out to sea from both East and West Heads and both of these points should be given a clearance of 100 metres. From East Head to westward into the channel, there are rocks below the surface up to 30m from the shore.
At night the Tory Channel entrance is marked by a sectored light on East and West Heads. There are two leading lights in Okukari Bay which, when in line, indicate the centre of the channel.
The interisland ferries give warning of their approach to the entrance by a general call on VHF channels 16 and 18. These ships must be given right of way, as once in the entrance any emergency manoeuvres to avoid small craft would be nearly impossible. If in the entrance at the time that the ferry passes, keep well to the side and there will be plenty of room.