The harbour porpoise is one of the smallest ocean mammals and has mostly a dark grey colouring, with a paler underneath. This cetacean is fond of quite shallow coastal waters, and can be spotted along Norfolk coast.
The local status is not well known. However, there have been increased sightings over the last decade, and the results of recent surveys suggest that the waters off the Norfolk coast are particularly important for this species. The main threats to porpoises are believed to be by-catch (accidental capture whilst fishing), over fishing, pollution, and environmental disturbance (e.g. noise from boats) and possibly climate change.