Crabs are Crustaceans and members of the Arthropod phylum. They have a hard exoskeleton surrounding their entire bodies which acts as a suit of armor. Most crabs use their powerful claws to fend off attacks and capture prey.
Some species such as the hermit crab scoot into empty snail shells and carry the shell on their backs. When threatened, they can disappear into the shell.
Other species rely on camouflage to hide from predators.
Most species of crabs can survive for short periods of time outside the water. Their shells hold enough water to keep their gills moist, therefore allowing them to breathe on land. Some crabs spend most of their lives on land.
Crabs range in size from barely visible to the giant coconut crab pictured here. Crabs can be found all over the world in a staggering variety of shapes and colors.