San Diego County, California, US
sandy beach, looks like a burrower
We found them trying to dig in dry sand. We ended up letting them go back into the ocean.
Thanks to Till Deuss and Arthur Anker for ID
Dead. About 1/2".
Emerita analoga, the Pacific sand crab or Pacific mole crab, is a species of small, sand-burrowing decapod crustacean found living in the sand along the temperate western coasts of America. It is found on exposed sandy beaches in the swash region of the intertidal zone.