'Jacksonville', a Los Angeles-class submarine was at periscope depth when it collided with the unidentified vessel yesterday.
"Damage appears to be limited to one of Jacksonville's two periscopes," 5th Fleet said in a statement.
"The reactor remains in a safe condition, there was no damage to the propulsion plant systems and there is no concern regarding watertight integrity," the statement said.
The periscope appears to be "slightly bent" according to initial reports, said 5th Fleet spokeswoman Lt. Marissa Myatt, who said the sub was keeping the damaged periscope raised.
"It's not going down the full capacity that they'd like it to, so they don't want to take any measures to degrade it any more," Myatt was quoted as saying by Navy Times.
A subsequent P-3 Orion surveillance aircraft search did not locate any vessels in distress and Myatt said the 5th Fleet had not been contacted by the vessel, which appears to be a small fishing vessel from reports.
'Jacksonville' is transiting the Persian Gulf and will head back into port to get the damages assessed, Myatt said. It is the sixth Navy vessel to sustain a collision at sea since May.
The 5th Fleet said the incident is under investigation. Investigators are attempting to identify the other vessel using the ship tracking system AIS.
'Jacksonville' left its home port of Pearl Harbour, Hawaii, on November 5 for a six-month deployment.
