On 8 January 2005, the USS San Francisco SSN-711 collided with an undersea mountain about 420 miles southeast of Guam while operating at maximum speed at a depth of 525 feet. 23 sailors were injured, one of them dying later. There was no damage to the nuclear reactor. The submarine was repaired at a cost of about $80 million and put back to sea on 10 October 2008, and returned to service in April, 2009.
That is the proper answer. 