In 2006, the USS Oriskany was deliberately sunk 22 miles off the coast of Pensacola, Florida. In doing so, the 44,000-ton aircraft carrier became the largest artificial reef in the world, lovingly nicknamed the “Great Carrier Reef.”

The USS Oriskany was launched on October 13, 1945, shortly after the end of World War II. The “Mighty O,” as it was also known, earned battle stars in both the Korean and Vietnam Wars, before being decommissioned in September 1976. Her service to the nation, however, was far from over, although her role would change from one above the waves to one below them.

After a lengthy environmental impact evaluation, the Environmental Protection Agency finally agreed that the retired Oriskany could be sunk to create an artificial reef and dive site. And so, on May 17, 2006, a team of Navy personnel sent the 888-foot ship to the ocean floor. It took the “Mighty O” 37 minutes to sink below the surface, at which point it went into the history books as the largest vessel ever sunk to make a reef.

It had taken the Navy more than three years and $20 million to prepare the Oriskany for its future as an artificial reef, so there was a lot riding on its success below the waves. Thankfully for all involved, including the aquatic life off the coast of Pensacola, it proved a huge success.

Within months, plants and shellfish had begun to attach themselves to the hulking vessel. And within a few years, the Oriskany had finished its conversion from a weapon of war to a fantastical underwater behemoth teeming with life.

Today its hull is frequented by whale sharks, tiger sharks, and hammerheads, while manta rays, octopuses and an occasional Warsaw grouper also drift through the vast sunken shell. Humans also flock to the artificial reef, which has become one of the United States’ bucket-list dive sites.

The ship sits in 212 feet of water, with some parts suitable for fairly inexperienced divers, and others only apt for seasoned pros. The top of the Oriskany’s island, or tower, lies at a depth of 80 feet, and is therefore accessible by recreational divers. Exploring further, however, is no simple task. Even the flight deck lies at a depth of 145 feet, and requires adequate training and equipment.

For the most adventurous and experienced divers, a strange labyrinthine world awaits inside the superstructure. Working their way through doors and down stairwells, these divers can swim deep into the hangar bays and the flag bridge, down into the depths of the sunken vessel.