No visit to New Zealand is complete without spotting its spectacular marine life.
Dolphins are a kind of toothed whale and are incredibly intelligent.
The cetaceans include both the baleen and toothed whales.
The spiral tusk typifies this extraordinary whale.
The exact function of the narwhal's tusk has troubled scientists for years.
Nigel Marven sets out on another adventure, this time focusing on grey whales.
A long spiral tooth sticking out the front of your face must be quite cumbersome.
One of the most wide-spread mammals on the planet, they inhabit every ocean.
Following Canadian scientists as they uncover a buried skeleton of a blue whale.
Up and down the coastline, Nigel Marven meets whale-watchers, scientists and researchers.