On December 7, 2016, the 75th anniversary of the attack on Pearl Harbor, at the conclusion of the remotely operated vehicle shakedown cruise, the team on NOAA Ship Okeanos Explorer explored this Japanese mini submarine, five miles off the entrance to Pearl Harbor. The sub was sunk on the morning of December 7, 1941. Ninety minutes before Pearl Harbor was bombed by air, the destroyer USS Ward fired on the mini submarine, sinking it. The sinking of the sub marked the first U.S. shots fired and the country's entry into World War II in the Pacific. For more information, click here. Video courtesy of the NOAA Office of Ocean Exploration and Research.