The Navy on Sunday revealed details of the final moments of seven sailors who died aboard a destroyer after it collided with a container ship near Japan — ripping open the warship and sending seawater gushing into the rooms where the men lay asleep.

“The damage was significant. This was not a small collision,” U.S. 7th Fleet commander Vice Adm. Joseph Aucoin said at a press conference in Yokosuka.

The Philippine-flagged ACX Crystal plowed into the far smaller USS Fitzgerald around 2:20 a.m. Saturday, “opening the hull to the sea” and rapidly flooding three large compartments that included two berthing areas for 116 crew members, Aucoin said.

The ship’s captain, Cmdr. Bryce Benson, was trapped inside his cabin, which was hit directly, Aucoin said. He survived but had to be airlifted to Naval Hospital Yokosuka, where he’s in stable condition.

The 300 brave sailors under his command quickly sprang into action to contain the flooding and save the boat from ending up at the bottom of the ocean — then navigated the damaged ship back into the busy port with only a magnetic compass and backup equipment.

“Heroic efforts prevented the flooding from catastrophically spreading which could have caused the ship to founder or sink. It could have been much worse,” Aucoin said.

“They are known as the ‘Fighting Fitz’ and the crew lived up to that name.”

But not everyone could be saved: Seven men were unaccounted for after the disaster, and divers searched through the wreckage Sunday to recover several bodies.

The Navy won’t name the men until their families have been notified, Aucoin said — although a TV news outlet in Charlottesville, Va., identified one of the missing seamen as local man Dakota Rigsby.

“Their loved ones are what makes this Navy great, so this loss is something we all do feel. The names of the deceased will be released soon,” he said.

Two other sailors are recovering in a hospital with minor injuries, he added.

It’s still not entirely clear what caused the collision — and Aucoin wouldn’t elaborate — but Japanese authorities are investigating “endangerment of traffic caused by professional negligence,” Reuters reports.