At the turn of the 19th century, during the Spanish-American war, the Spanish scuttled the steam gunboat San Quentin to block a shallow channel south-east of Grande Island.

The wreckage suggests a vessel 50-60m long. As the ship lies in only 12m of water, visibility and light are good. The ship's outline is easily discernable, although most of the wreckage has decayed and lies flat with the sand. The bow and stern are still fairly intact.

Marine life is rich and diverse.