Though actually a peninsula just south of Old Mazatlan and not an island, Isla de las Piedras (Stone Island) is usually accessed by boat, but can be reached by land as well. With just 4,000 residents, this is a spot Mexicans visit for a quiet, relaxing day at the beach. The waves are gentle enough for little swimmers, and many visitors rent snorkeling equipment or banana boats to enjoy the water. There are lots of beachfront restaurants, too.