Crayfish are freshwater crustaceans, closely resembling small lobsters, with a hard exoskeleton, a segmented body, and prominent claws. They have a two-part body consisting of a cephalothorax (fused head and thorax) and an abdomen (tail). Crayfish are found in various freshwater habitats like rivers, streams, and lakes, and some species can even burrow in muddy areas.