Dry Tortugas National Park is located off the coast of Florida. This is another National Park that is both unique and a little more difficult to get to. Like Isle Royale, Dry Tortugas requires a boat or seaplane trip to reach. Luckily, there are plenty of groups in the area that do offer such transportation. Dry Tortugas is probably most notable for Fort Jefferson – a massive historic waterfront building – as well as being an excellent spot for activities such as snorkeling.