Most eels prefer to live in the shallowest parts of the ocean. They live at the bottom of the ocean, sometimes in holes. Eels in the "Anguillidae" family come to fresh water to live there. Eels in the "Nemichthyidae" family swim about 500 m below the ocean surface. Eels in the "Synaphobranchidae" family live as deep as 4000 m below the surface.