Some crabs live in burrows on the sandy shore. Others live only in the water. The horseshoe crab, king crab, is more closely related to spiders than to crabs. The most common species are found on the eastern North American coast from Novia Scotia to Yucatan. Crabs wave their pincers in the air as a defense when they are disturbed.
Shore crabs hide under rocks and seaweed at low tide.
A crab shell is called a carapace. When a crab dies, its carapace is often washed onto the seashore. It is soon broken into small pieces by the crashing waves. The blue crab is the most common crab sold for food. The dolphin is an aquatic mammal closely related to whales and porpoises.