Coelom /ˈsēləm/: The body cavity in metazoans, located between the intestinal canal and the body wall.
what benfit do animals derive from having a coelm
"Coelom" is a fluid-filled body cavity in some animals, located between the gut and the outer body wall. It acts as a space for organs to be suspended and protected, as well as facilitating movement and expansion of internal organs. This cavity is present in organisms such as annelids, mollusks, and vertebrates.