‘Foreign submarine’ may have been whale

This has been a pretty bad year for the MSDF Aegis destroyer Atago. Back in February, the high tech warship accidentally rammed and sank a fishing boat, killing two civilians. Now, it turns out that submarine the Atago reported last week was most likely a whale:
The Defense Ministry announced on Sept. 14 that the Maritime Self-Defense Force destroyer Atago had detected “a periscopelike object” at a point south of the Bungo Strait off Cape Ashizuri in Kochi Prefecture.
But the ministry now suspects the vessel’s crew misjudged the object and that it was probably a whale, the sources said.
The ministry, however, also said that since there are no firm reasons for believing it was a whale, the case will likely remain unsolved.
How could they have mistaken a whale for a periscope? A Yomiuri article about the incident notes that it was the Atago’s captain who initially spotted the object:
At 6:56 a.m. Sunday, the captain of the Atago, who was standing on the port side of the deck, pointed to an area off the port beam.
“Isn’t that a periscope?” he asked.
The captain and his colleagues then observed the periscopelike object across choppy seas about one kilometer away.
After confirming that the presumed submarine was in Japanese territorial waters, about 20 kilometers off southwest Kochi Prefecture, the captain ran to the bridge and had the destroyer turn toward the spot where what was believed to be a submarine periscope had been sighted.
Was this a case of a foreign submarine, or a captain with an overactive imagination?

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