All five people aboard a submersible missing near the wreck of the Titanic died — likely in an instant — after their vessel suffered what the U.S. Coast Guard said Thursday was a "catastrophic implosion" in the ocean depths.

The somber announcement ended a multinational search-and-rescue operation that captivated the world since the tiny tourist craft went missing in the North Atlantic four days ago.

Rear Adm. John Mauger told reporters in Boston that analysis showed debris found on the seafloor, 500 meters from the bow of the Titanic, was consistent with the implosion of the sub's pressure chamber.