This cotidal chart shows the solar semi-diurnal or S2 tide. The colours represent the amplitude of the tide and the lines represent the phase. The most noticeable feature is the point near the Chatham Islands where the amplitude is zero and all the phase lines meet. This is called an amphidrome, a point where there is no tide at all. Its effect is to cause small S2 tides along the entire east coast of NZ (see the animation - 300KB).
Small S2 tides result in a reduced spring/neap effect. In fact, at Kaikoura where the S2 tide is only a few centimetres, the spring/neap effect is almost nonexistent.