I have just come back from a recent trip to New Plymouth and while I was there I happened to hear about how the wild seals in the area sunned themselves on the rocks at the old sea break at Port Taranaki. I ventured down there to take a look and was surprised at the number of them and how close I could get to them to get a few photos, mind you they did give a few protests at someone who got too close.
This is a free activity, but if you wish, there are boat trips, leaving from the port, that will take you out to the rocks just off the coast called Seal Rocks, where most of the seals can be found. Unfortunately I don't know the price of these trips.