Kaikoura is known as New Zealand's capital of whale watching. There you may choose any of the offered whale watching tours, either on vessel or helicopter. One can never become bored with whale watching since every other tour appears to be unique.
Once you encounter Giant Sperm Whales, another time you may see pods of Dusky Dolphins, including the largest species Orca and the smallest and rather rare Hector dolphins. Sometimes Fur Seals would reveal themselves or endangered Albatross would come into the sight.
But winter, especially June and July, is the most rewarding and exclusive season for whale watching, since only then one may spot migrating Humpback Whales, Southern Right Whales, Blue Whales and Pilot Whales which tend to come closer to the shores just in that time.