The Cordell Bank National Marine Sanctuary protects an area of 399 square nautical miles (529 square miles) off the northern California coast. The Sanctuary encompasses brilliant and diverse marine life, above and below the water.

The centerpiece of the sanctuary is an offshore granitic bank 4.5 miles wide by 9.5 miles long. The bank is located on the continental shelf, about 43 nautical miles (nm) northwest of the Golden Gate Bridge and 18 nm west of the Point Reyes Lighthouse. The actual sanctuary boundary starts just 6 miles offshore of the Lighthouse.

This rocky submerged island emerges from the soft sediments of the continental shelf, with the upper pinnacles reaching to within 115 feet of the ocean's surface. The continental shelf depth at the base of the Bank is roughly 400 feet.

Cordell Bank National Marine Sanctuary protects a very productive offshore area. The combination of ocean conditions and undersea topography creates a rich and diverse marine community.The prevailing California current flows southward along the coast, and the upwelling of nutrient-rich deep ocean water provides the foundation for a flourishing marine ecosystem.

The Sanctuary supports healthy resident populations and is a destination feeding ground for many migratory marine mammals, seabirds, and fishes. Invertebrates proliferate on the Bank and in the surrounding water column.

Cordell Bank is a unique wildlife watching destination at any time. The late summer and fall are the best time of the year to go out to the bank because of the abundant wildlife. From June until November, humpback and blue whales may be seen in the Sanctuary eagerly feeding. Throughout the year, seabirds from near and far feed in these bountiful waters. This attracts birders and whale watchers from around the world, to see species rarely seen so close to shore.