There have been three collisions, involving American SSNs in the Persian Gulf, during the last five years. On March 20th, a U.S. 24,000 ton amphibious ship (the USS New Orleans, LPD 18) collided with a submerged submarine (the 7,000 ton USS Hartford, SSN 768) in the narrow Straits of Hormuz. Fifteen sailors aboard the sub were injured, while a fuel tank on the LPD was torn open, and 25,000 gallons of fuel oil got into the water. Both vessels returned to port under their own power. The accident happened at 1 AM, local time.
In January, 2007, there was a minor collision between an American nuclear sub (the USS Newport News) and 1,100 foot long, 300,000 ton tanker (the Mogamigawa) in the Persian Gulf. There was some damage to the ship, in the form of a 108 foot long tear in the rear hull. The tear was four inches wide, and letting water in. The U.S. sub had its sonar dome, in the bow, badly damaged. But both vessels were able to make it back to port under their own power. An investigation revealed that the tanker was passing safely over the 360 foot long Newport News, but was going at such "high speed" (probably about 35 kilometers an hour), that a sucking effect was created, that pulled the 6,300 ton sub up until its bow banged against the bottom of the passing tanker. The Newport News was moving south, through the Straits of Hormuz, as was the Japanese ship. The tanker carried a crew of 24, the sub has 127 sailors on board.
In late 2005, nuclear submarine USS Philadelphia and a Turkish freighter collided in the Persian Gulf. In that case, the sub was on the surface, but the small radar signature of the surfaced sub did not show on the freighters radar until the ship was almost on top of the sub. The freighter and sub were on converging courses, with the freighter behind the sub. The collision, which had the 53,000 ton freighter running up over the back of the Philadelphia, on the right side, did not cause serious damage to either vessel. The sub suffered damage to its propeller, the fairwater plane, the rudder and the housing for the towed sonar array. The freighter got a hundred foot gash in its hull, right above the waterline. The two ships were entangled for an hour, but both made it back to port on their own.
The Straits of Hormuz, and the Persian Gulf in general, is a busy waterway, and there are always one or two U.S. SSNs there. That pattern, and all those collisions, may lead to changes in the way U.S. nuclear subs operate in these crowded waters. The Persian Gulf is 989 kilometers long, and the average depth is 50 meters (maximum depth is 90 meters). A U.S. SSN is about 18 meters from the bottom of the sub (the keel) to the top of the sail (the box like structure on top of the sub).