I still like the idea of using turbines that work off the current in the Cook Strait
Tidal stream turbines are still far from a mature technology.
One of the key issues is the marine environment is very harsh, especially in places with high tidal flows. Ain't going to be easy to install or maintain such a turbine.
At the same time as the above NZ, has some of the best onshore wind resource in the world, a technology that is fairly mature, and no need to antifoul etc.