The Ehime Maru and USS Greeneville collision was a ship collision between the United States Navy (USN)  USS Greeneville (SSN-772) and the Japanese fishery high school training ship Ehime Maru (えひめ丸) on 9 February 2001, about off the south coast of Oahu, Hawaii, United States. In a demonstration for some VIP civilian visitors, Greeneville performed an emergency ballast blow surfacing maneuver. As the submarine surfaced, she struck Ehime Maru, a fishery high school training ship from Ehime Prefecture, Japan. Within 10 minutes of the collision, Ehime Maru sank. Nine of her crewmembers were killed, including four high school students.