Largest of all the national seashores at 135,600 acres, with over five million visitors a year, Gulf Islands National Seashore offers plenty of room to go beachcombing and boat across 12 different units that are spread from the Gulf shores on the Florida Panhandle to Southern Mississippi. Eighty percent of the park is water. And the beaches, with their pure white sand, are heralded as among the most beautiful in the world. These crushed quartz shores are likened to spun glass, the grains of which have washed down over thousands of years, from the Appalachian Mountains and into the Gulf.