From the Navy Times:
An attack submarine and an amphib are out of action following a collision Friday during a nighttime transit through the narrow Strait of Hormuz.
The attack submarine Hartford and the amphibious transport dock New Orleans collided at 1 a.m. local time while moving into the Persian Gulf through the narrow passage between Iran and Oman.
Fifteen Hartford sailors were injured in the collision but were able to return to duty. No injuries were reported aboard New Orleans.
Details of the incident remain unclear. Hartford was "submerged but near the surface" at the time of the collision, according to Navy officials.
Today, Fifth Fleet Public Affairs released a statement, saying that both ships had arrived in Bahrain "to further assess and evaluate the damage that resulted from their collision at sea." They also released several pictures, showing Hartford's sail being significantly damaged (as in being knocked way off vertical). The damage to New Orleans appears to be entirely underwater.
Looking at the pictures, it would appear that the port side of Hartford's sail hit the starboard side of New Orleans' hull - and hit hard. Now, the Straits of Hormuz are notoriously shallow, and there is a lot of shipping going through not that much in the way of shipping lanes. It's way too early to judge what went wrong, but clearly something did.