The Maritime Self-Defense Force admitted Wednesday that it lost a $5 million unmanned submersible during a seabed study last year, with a nine-day search of the ocean floor yielding nothing.
The MSDF said it did not disclose the incident earlier because it judged there would be no impact on the environment.
According to the MSDF, the submersible, equipped with a camera and other functions, was being remotely controlled from its ocean research ship, the Nichinan, around 2 p.m. on Nov. 30 in the Tsugaru Strait between Aomori and Hokkaido when the cables connecting the device with the vessel broke.
“The vehicle was being used to survey the underwater terrain as well as water currents and temperatures,” an official at the Defense Ministry explained.
The unmanned craft was some 3 meters in length and some 2 meters in width and height. Weighing about 5 tons, the device apparently sank to the seabed.
Mariners searched the ocean floor in the area for the following nine days, but to no avail, according to the ministry official.
The MSDF has launched an investigation board to examine the details of the incident.
The submersible didn’t carry fuel so poses no threat of a leak and was not equipped with data-gathering gear that could be compromised, the MSDF reported.