Sipuncula, commonly known as peanut worms, are a group of marine invertebrates found in shallow coastal waters around the world. They have a soft, elongated body that can retract into a protective, burrowing structure. Sipunculans are typically benthic, meaning they live on or in the sea floor, and they feed primarily on organic matter and detritus. These creatures possess a unique body plan, featuring a distinct head with a retractable proboscis. Sipuncula are not segmented like annelids and are classified separately due to their unique anatomical features. They play an important role in the marine ecosystem by contributing to nutrient cycling and serving as prey for various marine animals.