Blue Swimmer Crab

Found over mud and sand bottoms, around mangroves, and in seagrass beds, of sub-tidal reefs, burrowing into the substrate when alarmed. Males blue, Females olive/brown

Brachyura crabs are considered true crabs, they have a short abdomen, four walking legs and a pair of clawed arms at the front.
Many thousands of species live worldwide in sea water, fresh water and on land.