There are lots of kinds of dolphin in the world, but Hector's are the only ones with that round, paddle-shaped back fin. Other dolphins have a fin shaped like a curved triangle. The rounded shape makes them easy to spot when they pop out of the waves.
They are playful even by dolphin standards. Hector's dolphins love riding the waves made by boats, jumping clear out of the water, and turning loops underwater. Sometimes whole groups swim alongside surfers and swimmers just to have a look.
Hector's dolphins live in small family groups of about 5 or 6, usually staying close to one stretch of coast. They have favourite bays they return to year after year. Scientists who study them can identify individuals by the unique nicks and shapes on their fins.
Like the yellow-eyed penguin, Hector's dolphins are carefully protected. Special areas of the New Zealand coast have rules about where boats can go and how fast, so the dolphins can swim and feed safely. There is also a smaller relative called the Māui dolphin, which lives only on one stretch of New Zealand coast and is one of the rarest dolphins on Earth.