The Royal Navy is deciding whether to repair or replace HMS Endurance
The Royal Navy's ice patrol ship HMS Endurance could have capsized or run aground off Chile following a major flood on board, a report has concluded.
The Ministry of Defence report said it was a "near loss" incident and "clarity of command" had been lost when the engine control room flooded in 2008.
Fifteen civilians were airlifted to safety from the Portsmouth-based ship.
Failures to identify "cumulative risk" factors were highlighted including lack of training, manpower and equipment.
The ship's mission is to patrol and survey the Antarctic and South Atlantic.
The flood happened when a valve opened suddenly and without warning because "air lines" attached to it had been incorrectly re-installed due to lack of knowledge among staff.
The ship began to roll to 25 degrees either side of upright and Navy personnel and the civilians began bailing out secondary floods.
Eventually the ship was anchored as it drifted over shallow water.
The civilians were airlifted off by the Chilean navy and the ship towed to Punta Arenas.
The report states: "Had the ship's anchor not taken hold over the only shallow patch that Endurance happened to drift over, there was a very real possibility that she would have been lost either by running ashore or by succumbing to the flood and the motion that she was experiencing."
The length of the ship's 18-month deployment was also criticised, with the report saying there were a number of "significant risks against capability" in the areas of staffing, equipment and training.
"One of the most significant deficiencies at all levels was the failure to identify the effect of cumulative risk," it said.
"As with most other incidents, this incident was not the result of one failing but a collection of contributory factors."
It concluded some risks could have been previously identified, because the engine room had flooded twice in the preceding eight weeks.
No-one was clearly in charge of risk-management, it said, and "clarity of command has been lost, with no one person within NCHQ [Navy Command headquarters] holding responsibility for the success of the deployment and being in a position to report robustly go/no-go items up the command chain."
The report makes 21 recommendations, which the Commander in Chief Fleet Admiral Sir Trevor Soar said he fully accepted.
He said the independent service prosecuting authority had decided there was insufficient evidence to take legal action against any one person.
"The Royal Navy has learned lessons from this incident," he said.
"The ship's company on board HMS Endurance at the time of the incident performed in an outstanding manner in the most difficult circumstances."
The ship was later brought back to Portsmouth, where the Navy is deciding whether to repair or replace it.