Horseshoe crabs live primarily in shallow ocean waters of Southeast Asia and the Atlantic coast of North America, at a depth of 10-40 meters. Sometimes they can be present in the estuaries.
used to be my pet...
In all seriousness though. The last photo makes me sick.
incorrect. horseshoe crabs are not crustaceans at all and in fact are more closely related to mites, spiders, scorpions, etc.