- Kingdom: Animalia
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Malacostraca
- Subclass: Eumalacostraca
- Superorder: Eucarida
- Order: Decapoda
- Suborder: Pleocyemata
- Infraorder: Brachyura
- Family: Portunidae
- Scientific name: Liocarcinus depurator
- Norwegian: vanlig svømmekrabbe
It may be confused with another common swimming crab, the flying crab. They both have three similar sized, blunt teeth on the carapace, between the eyes. There are five sharper teeth behind the eyes. As the name indicates, the paddle of the fifth leg has a blue or violet tint. The two arches of light spots on the back is also a typical feature of this species. The color varies from green or light brown to almost red. The carapace can grow 5 cm wide and 4 cm long.
The normal depth range is 5 to 150 meters, but has been registered on 450. It is most frequent on sand, mud or gravel.
It is known from the Mediterranean and the entire East Atlantic Ocean, from Africa to Norway.