Green shore crab walking on seabed with seaweed growing on its carapace

green shore crab seaweed seabed shore crab seafloor ecosystem carcinus maenas undersea invasive underwater ecology scuba snorkel aquatic strandkrab littoral crustacean under the sea water exoskeleton carapace dive diving nature invasion atlantic waters north sea swim ocean atlantic liquid otherworldly run animal marine escape crapace alien get away evade aqua scared