As many as 40 Navy divers, other personnel and a salvage ship from Pearl Harbor are supporting a survey of the debris fields 2 miles off Haleiwa where two helicopters apparently collided and crashed, killing 12 Marines.
The Coast Guard found a debris field Tuesday on the seafloor in 325 feet of water.
The Navy is studying what it would take to recover the debris, said Lt. Patricia Kreuzberger, spokeswoman for Mobile Diving and Salvage Unit 1.
"The determination has not yet been made on the scope or requirement for the recovery and salvage operation," Kreuzberger said Saturday.
The search for the 12 crew members of the two CH-53 Super Stallions, code-named Pegasus 1 and 2, was suspended Tuesday. The choppers belonged to Marine Heavy Helicopter Squadron 463, based at Kaneohe Bay.
However, the search for the wreckage of the two three-engine helicopters, each weighing 73,500 pounds, continues. The recovery effort is being conducted from a command post at Haleiwa Alii Beach Park, which remains closed.
Kaneohe Marines are aided by the USNS Salvor, a Navy salvage vessel, and divers from MSDU-1.
The dive unit played a key role in the recovery of the bodies of eight of the nine missing crew members and personal effects following the collision of the nuclear submarine USS Greeneville and the Japanese training fishing vessel Ehime Maru off Diamond Head in 2001.
The unit also was involved in the salvage of the cruiser Port Royal off Honolulu Airport's Reef Runway in 2009 and recovery of the older CH-53D Sea Stallion from Marine Heavy Helicopter Squadron 363 that crashed on a Kaneohe sandbar in 2011, killing one Marine.
Kreuzberger said the Pearl Harbor dive unit "provides combat ready, expeditionary, rapidly deployable Mobile Diving and Salvage Detachments to conduct harbor clearance, salvage, underwater search and recovery, and underwater emergency repairs in any environment."
Besides the Ehime Maru recovery mission, the Salvor, which belongs to the Military Sealift Command, participated in seven sea recoveries of submerged military aircraft, including an A-6E Intruder in Puget Sound, Wash., a UH-46D Sea Knight from a world-record depth 17,251 feet near Wake Island, a SH-60 Seahawk, an F/A-18C Hornet near San Diego and two F-16 Falcons in Korean waters and the Sea of Japan.
As the North Shore operation continues, civilian vessels are prohibited from coming within a mile of the crash site, 2.5 miles northwest of Haleiwa Small Boat Harbor.
The safety zone went into effect Wednesday and will remain in effect until Feb. 10 or until salvage operations are completed, the Coast Guard said.
A massive combined sea and shoreline search effort, which covered more than 53,600 square miles of ocean and shoreline between Haleiwa and Kahuku, was coordinated from the Haleiwa command post for five days following the crash, which occurred just before midnight Jan. 14.
It was suspended Tuesday at sunset when no survivors were located. A private memorial service for the 12 Marine aviators was held Friday at Kaneohe Bay.
All the wreckage and debris recovered will be moved to Marine Corps Base Hawaii for analysis as part of the military accident investigation. Because the crash involved military helicopters, the National Transportation Safety Board is not conducting its own investigation.
Besides crash debris, searchers recovered four life rafts carried by the two Super Stallion, each with a crew of six.
The Jan. 14 crash is the deadliest military training accident in Hawaii history.
In May a Marine MV-22B Osprey aircraft crashed at Bellows, killing two and injuring 20.
On Feb. 12, 2001, six Schofield Barracks soldiers were killed and 11 were injured when two Army Black Hawk helicopters collided during a routine night training exercise at the Kahuku Military Training Reservation on Oahu's North Shore.
On the night of the collision, helicopters were carrying soldiers from the 25th Infantry Division and equipment as part of a large North Shore exercise.
All six casualties came from a helicopter transporting an 8,000-pound Army Humvee in a sling. The main rotor blades of one Black Hawk severed part of the sling, sending the aircraft carrying the Humvee into a gulch.