Currents in the Cook Strait are made up of many different components, chiefly the tidal and storm driven currents.
This animation shows the major part of the tidal current, which causes strong currents in Tory Channel, the throat of the strait and Mana Island. This tidal current does not cause strong currents in Wellington Harbour, Queen Charlotte Sound or Clifford Bay. However, currents driven by storms can be as strong or stronger than the tidal currents and may completely change this picture. Unlike the tidal currents which are very predictable, the storm driven currents depend on local and distant weather and are very variable. Storms can cause very strong currents especially on exposed coastlines.