unknown crustacean from France

unknown crustacean from France

Observation - unknown crustacean from France - Global. Description: I saw this while on holiday in France. It was very large - I'd estimate 3-4cm long. It was crawling over the sea wall of a harbour. Would love to know what type of creature it is, no idea even what group it belongs to.

I saw this while on holiday in France. It was very large - I'd estimate 3-4cm long. It was crawling over the sea wall of a harbour. Would love to know what type of creature it is, no idea even what group it belongs to.