Mole Crab
The Mole Crab or Sand Bug Emerita talpoida lives on ( or rather in ) ocean beaches, burrowing in the surf zone, and at times free swimming. It is totally harmless and grows to 1.5". These odd and somewhat comical little creatures seem to do everything in reverse - they dig backwards, walk backwards, and swim backwards. Fishermen dig them up for bait.
Sand Bugs filter feed with their long feathery antennas, which are withdrawn into protective sheaths when not in use. Not the long eye stalks that allow the animal to remain completely buried, and the short powerful limbs. They are unable to walk in any conventional sense, but are powerful diggers, and also surprisingly swift ( if somewhat random ) swimmers.