Mud crabs, scientifically known as Scylla serrata, are large, edible crabs found in estuaries and mangroves, particularly abundant in the Indo-Pacific region. They are characterized by their smooth, broad carapace and powerful claws, which they use to crush prey and defend themselves. Mud crabs are known for their dark brown to mottled green coloration and their flattened hind legs, which aid in swimming. They are a popular seafood item and are commercially farmed in some regions.