Boca Chica Key is an island in the lower Florida Keys approximately 4.8 km east of the island of Key West, which itself is about 244 km south-west of Miami. The island is mainly composed of salt marshes and is the home to the largest Naval Air Station in south Florida.

The U.S. Navy's presence in Key West dates back to 1823 when a Naval Base was established to stop piracy in this area. The lower Keys were home to many wealthy shipping merchants whose fleets operated from these waters. This drew the interest of notorious pirates such as Blackbeard and Captain William Kidd, who used the Florida Keys as a base from which to prey on shipping lanes.

During World War I the base was expanded, and again during World War II at the end of which the Key West became home to submarines, destroyers and aircraft. After the war, the Naval Air Station on Key West was retained as a training facility and proved vital during the 1962 Cuban missile crisis. The Navy still maintains presence on Key West and on Boca Chica, but large sections of the island are today lying vacant.

Two years ago, a collection of seven submarine pits, covering 122 acres, were put up on sale at a price of $21 million. According to real estate website Ocseansir.com, the pits were used by Navy Air Station to house its submarine war ships during the Cuban Missile Crisis and has a “very colorful and distinct history”. The property includes seven finger cut coral canals that are 90 feet wide and over 25 feet deep, which are connected by a deep water entry channel that provides passage to Boca Chica Channel (Oceanside) and Key West Harbor (Bayside).

But are those really “submarine pens”? A Florida based blogger, Conchscooter, who explored the area in 2008 writes:

The thing about the "submarine pens" is that there are no structures alongside them, there are no docks, no cement no signs of any of the shoreside support systems that ships need when they come into port. So the conclusion one draws is that someone somewhere decided to hew out of the living rock a proposal to dock submarines 8 miles east of Key West Harbor across waters too thin to float a sub and instead of completing the channel first, they decided to carve out the pens? If true these things are the most expensive toilet seats the Navy ever sat on. But they do make a pleasant recreational area for Keys civilians, I must say.

Conchscooter poked around the internet but couldn’t find any mention of a submarine based at Boca Chica. The only submarine bases on Key West are the official docks at Truman Annex, where the Navy was based for a long time.

According to another source, the "pens" are actually canals carved out for waterfront property on a proposed Naval housing project that never happened.

Prior to October 1962, the Navy in Key West had planned to build dependent housing North of the Naval Air Station. The area would be a combination of housing on ordinary lots as well as houses which would be waterfront property for those who could afford to own a boat,.....or not. The large basin and canals were dredged out and the dredged material used to build a large breakwater on the West side of the basin. All the additional dredged material was spread out between the Southernmost canal and the Boca Chica viaduct connecting the Naval Air Station to Stock Island. This area was marked off with lines which would later be streets on each side of which housing would be built. The Cuban Missile Crisis effectively killed the housing project. The D Battery personnel lived in tent huts in this area for the next two years while awaiting the completion of their permanent site as well as the 727 Army barracks building at the Naval Air Station. There was even a mess hall built in the temporary area. The dredged area would later be used for fishing, diving, dumping of cars and other items which were no longer wanted. Over the years, people forgot about the intended use of the area and began speculating about the "real" use of the area. As with most stories, they are embellished every time they are told. The boat canals soon became WW2 submarine pens.

Sources: Wikipedia / Naval Technology. All images courtesy of Oceansir.com