Ten US sailors who were captured in January after straying into Iranian waters committed basic navigational blunders, were quick to surrender and some buckled under questioning, a damning probe released on Thursday said.

The report into the Jan 12 incident in the Persian Gulf highlights a string of leadership and procedural failings in Iran’s humiliating seizure of the 10 American sailors, with investigators saying the crews of the two captured boats had been derelict in their duties.

The sailors at times appeared haplessly lost at sea, with the engineer on one boat even resorting to an app on his smart phone to try to figure out the name of an unexpected land mass — which turned out to be Iran’s Farsi Island — only to find his phone displaying only a “long Arabic name” and no other information.

In all, nine navy personnel — three of whom were actually on the boats that were meant to head from Kuwait to Bahrain — have been disciplined or will face disciplinary action.

Iranian media broadcast humiliating images of the US sailors during their detention, showing them kneeling on their boats at gunpoint with their hands on their heads.

At one point during detention, a gunner from one boat thought about trying to escape, but “did not think of himself as a prisoner of war because the conditions were too nice”, the report stated. Although the sailors were held for less than 24 hours, the incident was a major embarrassment for the US Navy and President Barack Obama.

The United States carefully avoided escalating the situation, maintaining a conciliatory tone with Tehran days ahead of the implementation of a historic international deal over Iran’s nuclear programme.