The flattened legs of the crab act as streamlined struts. When they swim they use their legs as paddles and turn their bodies Page 4 Unit One Hydrodynamics Project Oceanography Fall 2001 19 sideways into the flow. This allows them to swim more easily through the water by minimizing the drag.

Can crabs actually swim?

Some crabs swim. Most crabs, like stone crabs and spider crabs, walk or run across the bottom. However, crabs in the family Portunidae have specially modified back legs called swimmerettes. These paddle-shaped legs rotate at 20 to 40 revolutions per minute, allowing the crab to quickly swim through the water.

How do crabs move in water?

Crabs use articulating, or movable, plates around their gills to help seal in moisture to prevent them from drying out. They also store water in their bladder, blood, and specialized pockets throughout their bodies. Behavioral adaptations also aid crabs with their terrestrial/aquatic transitions.