In 2005, the nuclear attack submarine USS San Francisco suddenly stopped dead in its tracks. The ship’s crew were thrown about, some over distances of 20 feet, and the majority of the 137-member crew suffered one injury or another—including one that would later prove fatal. Further inspection would explain what happened, and reveal that the submarine’s bow looked like a crushed soda can. USS San Francisco had run into an undersea mountain.

On that day, January 8, 2005, the San Francisco had been approximately 360 miles southeast of Guam, traveling at flank speed (more than 30 knots). The navigational charts used by the ship’s crew failed to show a seamount, or undersea mountain, protruding from the ocean floor. The sub smashed into it head-on.

The incredible thing about the incident: despite running into an immovable object at more than 30 miles an hour, at depth of 525 feet, the San Francisco didn’t sink, nor did it experience a reactor malfunction. Even more incredibly, the submarine was able to move under its own power back to port on the island of Guam. All of that is directly attributable to safety actions the U.S. Navy had taken four decades earlier.

Read More- Popular Mechanics