The harbour porpoise is the smallest cetacean found in Icelandic waters, and is actually one of the smallest marine mammals in the world. The harbour porpoise is not a dolphin but belongs to a family called Phocoenidae. Only seven species of porpoises exists in the world today and the harbour porpoise is the most widely distributed one, but the harbour porpoise is the only porpoise species living in the North Atlantic Ocean. Porpoises have in common a short and stocky body which enables them to limit heat loss in cold waters. Apart from their characteristic body shape, the porpoises can be recognized from their round and oval head which lacks the pronounced snout, the common characteristics of dolphins. The harbour porpoise is extremely fast and agile swimmer which can make them very challenging to spot out at sea. However, they are commonly spotted in whale watching tours from Reykjavík, usually not far out off the harbour.