We spent Easter on the beach and had a great time. This park has nice amenities and there was a sculpture show going on, so there were cool sculptures in unexpected places. We rented chairs and an umbrella, which were a bit steep in price, but a good idea if you intend to spend the whole day as we did. The beach consits of sharp coral so bring water shoes! The water was beautiful and clean and we were able to paddle our little raft out to some rocks and explore. Admission to the park is just a few dollars so it is worth visiting on foot or by bike even if it is just to wade or visit the fort.

Great scenery, nice picnic areas, clean beach only problem is ROCKS! but if you can get by the rocks you will enjoy the day. Clean bathrooms, many outside fresh water showers. Bring your own chairs if you want because the rentals can be VERY expensive. Birds can be a problem if you sit next to someone who leaves food
around or feeds the birds. $6.50 for me and my girlfriend for the whole day was cheap as opposed to South Beach. I saw plenty of trees so there is a lot of places with shade. It is the best beach in Key West.

The beach at Fort Zachary consists of more than just sand. Hundreds of Australian Pines add an air of quiet and solitude to the setting. Locals know this is the best place to hang a hammock for the day, in the cool shade with the beach as a background. Do bring aqua shoes; there are rocks just like everywhere else in the coral rocks known as the Florida Keys.

The place is not "as nature intended". The beach is dredge spoils piled up there by the navy. The fort was originally a small island to itself. The park service was making a big effort to plant native plants there, I assume they still are.
This isn't hearsay, I worked for FPS, who wished the fort would just go away so they wouldn't have to spend money on it, and just use the beach for a cash cow. This is prob. still the case.
The fort should be seen if you have any interest in history - it's the reason the "conch republic" stayed in Union hands during the civil war - Union troops took it over before secession, and they had the entire town under their guns. Modified for the Spanish American Period, slight modifications made for WWII, during the Cuban Missle crisis antennae were mounted on the old span-am batteries. Climb up there and you can see civil war cannons half buried in the later concrete work. They are stacked like wood all the way down to the foundations.