A reef teeming with more than 500 species of marine life, a pirate-hunter shipwreck, and a 144-year-old lighthouse all sit just four nautical miles offshore from Islamorada in the Florida Keys.

Built in 1873, Alligator Reef Lighthouse stands guard in honor of its namesake, the USS Alligator. In 1822, just two years out of the shipyard, the Navy schooner was on rounds to recapture and free ships that were taken in the pirate-heavy seas of the Caribbean. At Alligator Reef, a notoriously difficult area to navigate, the young ship ran aground.

The seamen struggled desperately to save it, but eventually had to give up the ship. To keep it out of pirate hands they stripped it of all salvageable material and set it afire. The ship soon blew up, leaving only shards and flotsam at the bottom of the shallow waters.

Many other vessels have been plunged into the depths by this reef, eventually leading to the establishment of the lighthouse station. The freestanding rig and its lantern cost $185,000 at the time, an amount equal to over $3,750,000 in today’s dollars. The structure required 12-inch thick iron pilings to support it, slammed into 10 feet of coral by a specialized hammer that weighed (literally) a ton.

Despite its inauspicious beginnings, the 136-foot lighthouse still stands nearly a century and half later. At an average depth of 20 feet, the surrounding reef is ideal for snorkelers and divers looking to explore Florida’s Caribbean coast. There are spiny lobsters, parrotfish, barracuda, and abundant coral all in a jumbled graveyard of shipwrecks. Somewhere down there are the remains of the USS Alligator.