Marine worms are a diverse group of invertebrates that live in ocean environments. They belong to various phyla, including Annelida, Nematoda, and Sipuncula. These worms can be found in different habitats, such as sandy or muddy sea floors, coral reefs, and even deep-sea environments. They play essential roles in the ecosystem, contributing to nutrient cycling and serving as food for many marine animals. Most marine worms have elongated bodies and can vary greatly in size and appearance. Some, like polychaetes, have bristle-like structures called setae that help them move and burrow. Others, such as lugworms, create U-shaped burrows in the sediment. Marine worms are important indicators of environmental health and biodiversity in marine ecosystems.