Common Dolphin Delphinus delphis
Common dolphins have distinctive colouring with multiple colour bands along their sides. Predominantly black or dark grey in colour, forward of the dorsal fin their flanks have a flash of yellow whilst behind the dorsal fin it is white. This colouration forms a beautiful hourglass pattern on their sides. Image: Natural England/Rebecca Walker (Flickr).
Find out more: Whale and Dolphin Conservation, The Mammal Society, Suffolk Wildlife Trust, iNaturalist