A British nuclear-powered submarine collided with rocks beneath the surface of the Red Sea, damaging its sonar, the military said late Tuesday. The HMS Superb hit an undersea mountain while diving in the northern Red Sea on Monday, the Ministry of Defense said. There were no casualties and the ship has now safely surfaced, the ministry said in a statement. It added that the vessel remains watertight and that its nuclear reactor was "completely unaffected." The vessel does not carry nuclear weapons. The Superb's Web site said the submarine, commissioned in 1976, has completed an "intensive maintenance and upgrade period" and would spend a short period on a training mission before its main deployment in 2008.