A quite slender fish, the Sand Goby, Pomatoschistus minutus, is not very easy to identify and can be initially confused with the Common and Painted Gobies. It is a light sandy colour and males have an almost black dot at the rear edge of the first dorsal fin. It may reach 9cms but more commonly it is about 6cms. Widespread around UK coasts on areas of sand down to the 20m mark. In my experience, they readily hide in or under empty shells or discarded items.
Sometimes called the One-spotted Goby.
St. Abbs Marine Reserve, North Sea