Along with the ships are ten American sailors, who are now being detained by Iran. From NBC:
The officials said it’s unclear whether the 10 American sailors aboard two small riverine vessels had strayed into Iranian territorial waters before they were captured.
The sailors were on a training mission around noon ET when one of the boats experienced mechanical failure and drifted into Iranian-claimed waters, officials added. The Iranian Coast Guard took them into custody, although the crew has been described as being safe.
According to the Associated Press, Pentagon officials are in contact with Iran and have received assurances the troops will be returned swiftly.
Pentagon spokesman Peter Cook told The Associated Press that the boats were moving between Kuwait and Bahrain when the U.S. lost contact with them.
“We have been in contact with Iran and have received assurances that the crew and the vessels will be returned promptly,” Cook said.
The AP is also reporting that Secretary of State John Kerry contacted his counterpart in Tehran, Iranian Foreign Minister Mohammed Javad Zarif, in an attempt to resolve the issue.
UPDATE: J/K says Iran