Presents background information about the sinking of the Spanish galleon, Atocha, in 1622 and describes efforts to locate the wreck and successfully salvage its treasure more than 300 years later.

"Off the coast of Florida, 200 feet beneath the waves, a massive aircraft carrier lies on the bottom of the ocean floor. Once an unsinkable ship, the Mighty O is now an underwater city teeming with marine life. After 25 years of service in the Navy, the ship took on a new mission as an artificial reef."