Some of the 12 Hawaii Marines who perished in an apparent nighttime fiery crash of two big CH-53E Super Stallion helicopters at sea off Waimea Bay on Jan. 14 have been recovered, the Marine Corps has confirmed.

A salvage and recovery operation endeavored to make progress Monday, meanwhile, with the USNS Salvor slated to head out to the debris field with specialized dive equipment.

“The families have been given the information (about remains recovery),” said Capt. Tim Irish, a Marine spokesman, declining to provide any more details.

“We have a very detailed plan in place to handle any of our brother Marines as we retrieve them and then bring them back to their families, wherever they would like, in a dignified fashion,” Irish said Monday in a phone interview.

The fallen were members of Marine Heavy Helicopter Squadron 463 at Kaneohe Bay. Some family members of the deceased Marines have been out to Oahu from the mainland. The crash was among the deadliest military noncombat accidents in Hawaii history.

A debris field was found on the seafloor in about 300 feet of water 2 miles offshore — a depth that is making a recovery more complicated, the Marines said. The Navy Personnel Command said Navy divers perform ocean, harbor and combat/expeditionary salvage operations in up to 300 feet of water.

Divers from Mobile Diving and Salvage Unit 1 needed equipment from Key West, Fla., for use on the 255-foot rescue and salvage ship Salvor. Rough seas also pushed back the Salvor’s departure to the site of the crash from Saturday to Monday, the military said.

Irish said the specialized equipment now on hand includes the ability to mix gases for dives to deeper depths. At the same time, divers have been training to acclimate to those depths, he said.

“As I understand the systematic aspect of it, you wouldn’t just want to start diving at 280 (feet) just to discover you are going to have to dive past 300 and need that training and acclimatization gear anyway,” Irish said. “So that was just another piece that had to fall into place.”

A second Navy ship, the 226-foot fleet ocean tug USNS Navajo, also is expected to assist, Irish said.

“Salvage and recovery is being done as efficiently as possible,” he said. It also is being done with “a goal of the aircraft mishap board being able to figure out exactly what did happen and then, of course, not risking any lives in the effort to conduct salvage and recovery.”

The Coast Guard said the Salvor was to use sonar and a remotely operated vehicle on board to locate the aircraft.

“Salvor does have a crane that could pull the aircraft out of the water, but no decision has been made for that operation,” Sarah Burford, a spokeswoman for the Navy’s Military Sealift Command, said in an email Saturday. “The first step is to get the ship out to the site and to get the wreckage mapped; then a decision will be made as to how the recovery operation will proceed.”

The III Marine Expeditionary Force in Okinawa, Japan, the higher headquarters for Marine Corps Base Hawaii, said upward of 80 personnel will be supporting the recovery and salvage operations, including debris field survey and dive system preparation.

A spokesman for the command, 1st Lt. Joseph Butterfield, said about 40 personnel are supporting from MDSU-1; 26 civil mariners comprise the crew of the Salvor; and 10 Marines are supporting with shoreline search and investigations.

“We would like to express our gratitude for ongoing support to recovery and salvage operations. We thank everyone for their contributions,” Butterfield said in an email.

Six Marines were aboard each aircraft during the training accident. One instructor pilot was paired with a student pilot, and two instructor crew chiefs were paired with two students. The training involved the use of night-vision goggles and a simulated scenario meant to practice loading and moving troops.

Star-Advertiser reporter Gregg K. Kakesako contributed to this report.