The horseshoe crab is a marine animal whose exoskeleton – its shed skin – is regularly found on beaches and along the shores of estuaries. In spite of their name, they are not true crabs, but are much closer relatives of spiders. Ancestors that looked like modern species swam in our oceans more than 300 million years ago. Today’s horseshoe crabs spend their time walking on the bottom, searching for worms and other marine creatures they eat. Horseshoe Crab legs are totally beneath their exoskeleton, protected by the canopy formed by their upper exoskeleton as they hunt for food. They are capable of swimming, but when swimming they move through the water upside down at about a 30 degree angle. In spite of their long, pointed tail that appears dangerous, horseshoe crabs are harmless to humans.