MANILA, Philippines—Divers of the Philippine Coast Guard and Philippine Navy are undergoing physical and psychological preparations for the retrieval of hundreds of bodies believed trapped inside the M/V Princess of the Stars that sank off Romblon at the height of a typhoon last July.

Coast Guard officials said on Tuesday that retrieval of bodies has been set to begin in a few days.

Dr. Ted Esguerra, a Coast Guard doctor, said an underwater grave would be a grisly sight. “The Coast Guard divers are not shocked anymore. They are used to it,” Esguerra said, but added that they would still need to guard against divers sickness and trauma.

Lt. SG. Gary Dale Gimotea, Coast Guard spokesman, said that of the 864 passengers and crew members on the ship, 515 passengers remain missing. Only 33 survived and 349 bodies were initially recovered from the area and surrounding coasts.

The Coast Guard hopes to find many of these bodies inside the sunken ship.

Recovery of the bodies was suspended when it was revealed that toxic chemicals were inside the cargo hold. Over 400 drums of the pesticide endosulfan were extracted earlier this month.

Since four months have passed, the bodies were expected to be in an “advanced stage of decomposition,” Esguerra said.

The divers should expect the worst. No matter how hardened the divers were to such operations, it could still take a toll on the body and the mind, he said.

“They will have debriefings before and after the dive. That is how you maintain sanity,” he said.

Gimotea added that the work of taking out the bodies would be a dangerous, complicated, and drawn-out task. It will require well timed and choreographed team work.

The Coast Guard estimated that at least 50 divers from private and public agencies will be needed in the recovery operation.

Gimotea said initial surveys indicated that remains were concentrated in a part of the vessel, 60-120 feet underwater.

Divers would have limited time to extract them, Gimotea said, explaining that a diver going down 60 feet could safely stay for around 45 minutes, while divers who would go down 120 feet could stay only for 15 minutes.

Although the final details still needed to be threshed out, Gimotea said they estimated that it would take four divers to extract one body.

They will use a net to secure the remains and then place it inside a body bag supplied by the Department of Health.

Divers will be advised to take a 24-hour-rest between dives to avoid diving sickness.

“You plan your dive. If you don't follow (the plan), accidents might happen,” Gimotea said.

The remains will be shipped to Cebu City for identification by the National Bureau of Investigation.

The Board of Marine Inquiry, which investigated the sinking, blamed the ship's captain for the tragedy. It also held Sulpicio Lines, the owner of the vessel, accountable, and had recommended the cancellation of their license to provide passenger and cargo shipping services.

The MV Princess of the Stars sank off Simbulan Island, Romblon last June 21, at the height of typhoon "Frank."