Just north and west of San Francisco Bay a large expanse of Pacific Ocean along with nearshore tidal flats, rocky intertidal areas, wetlands, subtidal reefs, and coastal beaches were designated in 1981 as Gulf of the Farallones National Marine Sanctuary. This 1,255 square mile area (948 square nautical miles) is larger than the state of Rhode Island. The Farallon Islands, 30 miles (26 nautical miles) west of the Golden Gate Bridge in the south central part of the sanctuary, are a national wildlife refuge, offering resting and breeding sites for marine mammals and seabirds, lured by nutrient-rich waters. The sanctuary has thousands of seals and sea lions, and is home to the largest concentration of breeding seabirds in the continental U.S Visitors to Gulf of the Farallones National Marine Sanctuary can enjoy activities such as camping, tidepooling and surfing.