I know this photo is poor, but you can make out the coloration and those incredible hairs on the legs. It was observed in a rocky intertidal area. Sally lightfoot crabs were nearby.
Small, white spots, about 6 of them, on rocks right next to water, orange claws, purple and gray
Looks like a thin-shelled or striped rock crab.
San Diego County, California, US
This small crab was hiding in the seaweed and other algae growth on a rock at a super low tide. You can see its front pincers here
Grapsoidea is a superfamily of crabs. These crabs are well known and contain many taxa which are terrestrial (land-living), semi-terrestrial (taking to the sea only for reproduction) or limnic (living in fresh water). Another well-known member with a more conventional lifestyle is the Chinese mitten crab, Eriocheir sinensis.