The protected marine area of shoal Peterno Tor is located off the coast of Castel Fusano. It is constituted by a rocky formation, covered by plant and animal organisms. It is a real island under the sea whose depth part from 18 m below the sea level. The area is declared its vertices by 4 buoys.
The marine protected area consists in a single general reserve zone situated about 4.5 nm to W of Torvaianica.