As an American destroyer cruised off the waters of Japan in clear weather after 2 a.m. Saturday, only a few dozen of the crew of 350 were likely to be awake: standing watch, keeping the engines running, manning the bridge.
Then, Navy officers with decades of experience at sea say, there were probably minutes of sheer terror aboard the Fitzgerald before the collision with an enormous container ship that killed seven sailors.
“My guess is they suddenly saw the lights of the other ship coming toward them and tried to veer off,” said retired Adm. James G. Stavridis, whose book “Destroyer Captain” recounts his time commanding a similar ship in the mid-1990s. “Suddenly your ship is sinking under you. It’s terrifying.”
Navy leaders on Sunday hailed the efforts of the surviving sailors who struggled to seal off compartments and pump out the water that poured in through gaping holes torn in the starboard side.
“Heroic efforts prevented the flooding from catastrophically spreading, which could have caused the ship to founder or sink,” said Vice Adm. Joseph P. Aucoin, commander of the Navy’s Seventh Fleet. “It could have been much worse.”
With the aid of tugboats, the Fitzgerald returned on Saturday to its port, the American base at Yokosuka, Japan, south of Tokyo.
As hundreds of anxious spouses, children and fellow sailors waited for word, Navy divers entered flooded compartments below decks and recovered the bodies of seven sailors, according to former Navy officials.
The Navy released the names on Sunday night of the seven sailors who were killed. The victims were all located in flooded berths, the Navy said.
They were identified as Dakota Kyle Rigsby, 19, of Palmyra, Va.; Shingo Alexander Douglass, 25, of San Diego; Ngoc T. Truong Huynh, 25, of Oakville, Conn.; Noe Hernandez, 26, of Weslaco, Tex.; Carlos Victor Ganzon Sibayan, 23, of Chula Vista, Calif.; Xavier Alec Martin, 24, of Halethorpe, Md.; and Gary Leo Rehm Jr., 37, of Elyria, Ohio.
The Navy said the collision inflicted significant damage to the destroyer above and below the water line, flooding berths, a machinery area and the radio room.
Photographs showed the side of the Fitzgerald caved in about one-third of the way back. Among the compartments that flooded were cabins where 116 sailors were sleeping, Admiral Aucoin said.
A collision of a United States Navy ship resulting in fatalities is extremely rare; veteran seamen could recall only a handful in recent decades.
Admiral Aucoin said he would appoint a flag officer to conduct one of several investigations that will seek to establish exactly what happened and to apportion responsibility.
The Navy will conduct a separate safety investigation intended to find lessons on what might be done differently to reduce the risk of such accidents in the future.
The United States Coast Guard will also carry out a marine casualty investigation, Admiral Aucoin said, evidently because the crash involved a commercial ship, the 29,000-ton ACX Crystal, registered in the Philippines.
According to Navy veterans, the main investigation ordered by Admiral Aucoin will compile a minute-by-minute timeline of everything that happened before the collision, probably beginning at the moment the ACX Crystal appeared on the Fitzgerald’s radar.
Investigators will interview everyone who was on duty that night and assess their training, experience, competence and sleep schedule. They will also assess the performance of the radar, which stores a recording like the “black box” on an aircraft.
They will determine whether anyone on the ship’s bridge pulled the collision alarm, a switch that would have caused an extremely loud signal to sound, directing every crew member to rush to specifically assigned emergency stations on the ship.
“The crew is highly trained in damage control,” Admiral Stavridis said. “That includes fighting fires and fighting flooding.”
The mother of a sailor who survived the collision, Mia Sykes, said her son kept diving to try to save his shipmates until the flooded berth began running out of air pockets, while others — believing the ship was under attack — hurried to man the guns.
Ms. Sykes, of Raleigh, N.C., told The Associated Press that her son, Brayden Harden, 19, was knocked out of his bunk by the impact. She said Mr. Harden told her that four men in his berth, including those sleeping on bunks above and below him, died, while three died in the berth above his.
The investigators’ attention will be focused in particular on the Fitzgerald’s commander, Bryce Benson, who was in his stateroom on the destroyer’s starboard side when the Crystal’s bow struck right at that point. He was injured and airlifted by a Japanese Coast Guard helicopter to Yokosuka, along with two other crew members, the Navy said.
“His cabin was destroyed. He’s lucky to be alive,” Admiral Aucoin said of Commander Benson, 40.
Before retiring for the night, Commander Benson would have signed routine “night orders,” updating the standing orders he had issued to the entire crew. They would almost certainly have dictated those on watch to wake him if another ship was expected to pass close to the Fitzgerald in the busy shipping lane south of Tokyo.
The fact that he was in his cabin when the collision occurred suggested that there was very little warning before the accident, Navy veterans said.
Some captains include in the night orders a generic admonition, “Call me if you’re in doubt.” Most ask to be awakened if another vessel’s closest point of approach, or C.P.A., is less than a certain set distance.
“My orders were always to call me if the C.P.A. was less than 5,000 yards,” said Bryan McGrath, a national security consultant who commanded a destroyer in the Atlantic from 2004 to 2006.
Such orders, in the kind of ocean traffic in that part of the Pacific, would make for much-interrupted sleep for the captain. But it reflects “the unique status of the captain of a Navy ship in American society — absolute authority, and absolute accountability,” Mr. McGrath said.
“It doesn’t matter if you’re asleep when the collision occurs,” Mr. McGrath said. “Why didn’t the watch standers call you? Were they not trained properly? Ultimately, it’s all your responsibility.”
Several experienced ship commanders said the captain is all but certain to be relieved of command because of the accident.
“It’s a terrible, swift sanction, but it sends a message to everyone else in the fleet — make sure you’re training harder, make sure they call you when another ship is approaching,” Mr. McGrath said.
Admiral Stavridis, the former destroyer commander, who is now dean of the Fletcher School of Law and Diplomacy at Tufts, said it was too early to speculate about the cause of the collision.
The Fitzgerald, under international maritime rules, would be expected to give the Crystal the right of way because it was on the destroyer’s starboard side when they hit. But Admiral Stavridis said the container ship “may have carried out some bizarre maneuver” before the crash.
Marine traffic records show the Crystal made a series of sharp turns about 25 minutes before the collision, which in crowded seas might have caused a cascade of maneuvers by other vessels as they tried to avoid one another.
Whatever the ultimate findings, Admiral Stavridis said, “My heart is really with the captain. He’s got a rough passage ahead, to put it in nautical terms.”
Marc Tuell, who served as a personnel specialist on the Fitzgerald from 2010 to 2013, when he retired from the Navy, said it was deeply disturbing to watch the video of the damaged ship being towed to port in Japan.
“I was putting myself in the mind-set of what the crew is going through,” said Mr. Tuell, of Deltona, Fla., who now works at a Toyota dealer. “It’s pretty heart wrenching, having walked those decks for three years.”