Fort Zachary Taylor State Park
For a little history with your day at the beach, head to Fort Zachary Taylor State Park. This impressive 54-acre park at the tip of Key West not only has a good beach, but an enormous stone fort dating back to the mid-19th century. The sand here isn't as soft as other beaches, but it's still okay.
The swimming here is excellent and due to the prevailing water currents the visibility makes for fantastic snorkeling with lots of colorful fish in the water. If you need beach gear, a shop in a bamboo shack rents chairs and umbrellas, as well as all snorkeling gear. A small café offers local specialities, snacks and cold drinks.
Take a break and visit the fort. Guided tours are available at 11 a.m., and the fort is well worth a stroll. As you walk around, be sure to check out the extensive collection of Civil War-era cannons. Climb the stairs to the top of the wall; the view from the walls of the fort over the Key West area is magnificent.