Crustacea are a diverse group of aquatic animals that include familiar creatures like crabs, lobsters, and shrimp. They are characterized by their hard exoskeleton, which protects their bodies, and jointed legs that help them move. Crustaceans can be found in various environments, from oceans to freshwater lakes, and they play important roles in the food chain. These animals are also known for their unique life cycles, often starting as tiny larvae before growing into adults. Some crustaceans, like barnacles, attach themselves to surfaces, while others, like krill, swim freely in the water. Overall, crustaceans are essential to marine ecosystems and human diets.