"It's a plot worthy of a Hollywood action movie: 40 years ago, the U.S. Navy carried out a daring mission to retrieve a top-secret film capsule that had settled more than 16,000 feet (4,876 meters) underwater on the ocean floor."
"At the time, the expedition was the deepest undersea salvage operation ever attempted. Documents released by the Central Intelligence Agency on Wednesday
detail the capsule's incredible recovery, using what was at the time the
Navy's most sophisticated deep-sea submersible. On July 10, 1971, a classified U.S. satellite, code-named Hexagon,
attempted to return a mysterious 'data package' to Earth by ejecting a
capsule over the Pacific Ocean. The capsule's parachute failed, and the
canister slammed into the water with an excruciating 2,600 G's of force."
"Since these satellites preceded today's era of digital technology,
Hexagons recorded images on film, sending them back to Earth in capsules
that re-entered Earth's atmosphere and were recovered within a
designated zone near the Hawaiian Islands in the Pacific Ocean. During the first Hexagon mission in 1971, the parachute attached to
one of these capsules broke. The capsule sank to a depth of about 16,400
feet (almost 5,000 meters) in the Pacific... At that time, no object the size of the film canister had ever been detected by sonar and been searched for underwater."
You can read more at NBC News HERE. I wrote HERE a year ago when the first public references to this event were initially made.