The first thing you’ll notice about Dry Tortugas is that it’s surrounded by water; the park got its name because there was no fresh water available while building Fort Jefferson, which is the centerpiece of the park. The fort was never completed, although it was used as a prison during the Civil War, so it’s historically significant, in addition to just being crazy. It’s not every day you see a giant fort out in the middle of the super clear, blue ocean. Navigating to the island was treacherous back in the day, so it is surrounded by shipwrecks you can snorkel up to. You can go on guided tours of the fort as well, but since this park is in the middle of the ocean, facilities are limited.