Nereis is a genus of marine polychaete worms, commonly known as ragworms. They are characterized by their long, segmented bodies and bristle-like structures called chaetae, which help them move through the water and burrow into the sediment. Nereis species are found in various marine environments, from shallow coastal waters to deeper ocean floors. These worms play an important role in the ecosystem as they are both scavengers and prey for various marine animals. They are often used as bait in fishing, particularly for species like flatfish and striped bass. Their presence indicates a healthy marine environment.