About 70 miles from Key West, the Dry Tortugas National Park is comprised of seven islands, straddling the Gulf of Mexico, Caribbean Sea and Atlantic Ocean. This remote treasure is only accessible by seaplane, private boat or the Yankee Freedom II--a high-speed catamaran that departs from Key West. The shallow waters surrounding the islands are perfect for snorkeling amid the ruins of Fort Jefferson. Tour the fort to learn about its construction and Civil War prisoners like Samuel Mudd--the doctor who assisted John Wilkes Booth after his injury. Prices start at $165 and include park entrance, meals, snorkeling and tour of Fort Jefferson.