How do marine worms move?

Many marine worms are sessile, which means that they remain stationary for their entire lives.  Others crawl around on the mud of the ocean floor by propelling themselves with their entire body surface.  There are three ways they do this: by gliding on microscopic hairs, by muscular contraction that begins at the head and moves down the body, and by wiggling the body much as a snake does.  There are a few species of worms that can swim, including the strong-swimming leaches.