The Arachnids of the Sea
With over 6500 different species, crabs are one of the most varied aquatic dwellers in the world. These crustaceans have a thick exoskeleton to protect their inner organs with an oblong, square, or diamond-shaped central body cavity, four sets of legs, and one pair of pinchers. Crabs range in size from the tiny pea crab measuring only 10-15 mm (0.4-06 inches) to the giant Japanese spider crab, which can grow up to 4 meters (13 feet) across.
Diving with crabs is a common activity and can occur in nearly every body of water, both salt and fresh. In fact, about 850 crab species are freshwater crabs. Look for crabs scurrying across the sand or grassy bottom and hiding in cracks and overhangs on the rocky or coral reef. Crabs are particularly abundant in the tropics. To see where you can go diving with crabs, explore the dive site map below.