Some are still locked together in embraces, a freeze-frame of panic as the water rushed in and the ship sank. The hair of female corpses ripples in the current, framing pale faces.

At times, heavy sediment in the water can make flashlights useless and it is almost total darkness inside the South Korean ferry, which has flipped upside down on the seafloor. Divers must stretch their hands into the void to search for bodies. There's constant worry their lifeline to the surface, a 100-meter oxygen hose, will get snagged or cut as they swim deeper through the wreck's maze-like hallways.

For nearly a week now, dozens of divers have battled fast currents and cold waters — as well as exhaustion and fear — to pull out a steady stream of corpses. As they go deeper into what's become a huge underwater tomb, they're getting a glimpse of the ship's final moments April 16 before it capsized. More than 300, most of them high school students, are feared dead.

"They can see the people's expressions at the instant" the ship sank, Hwang Dae-sik said of the team of 30 divers he supervises for the Marine Rescue and Salvage Association, a private group of professional divers who've joined Korean navy and coast guard divers in the search and rescue effort. "From the bodies' expressions, you can see they were facing danger and death."

Divers descend about 30 meters (100 feet) down and enter the ship through windows they've broken with hammers.

Han Yong Duk, a 33-year-old diver, said that visibility was often so poor that divers had to feel their way along the outside of the ship to find windows they could smash. One diver tried to hit the ferry with a hammer but only connected with steel, not glass.

Another civilian diver said that sometimes it was pitch black; other times there was less than 20 centimeters (a foot) of visibility.

"I got around by fumbling in the darkness to try to find things with my hands," said Cha Soon-cheol, who spent five days helping with searches. Swimming against the strong currents exhausted him.

Once inside the ship, divers have to dodge floating debris — passengers' belongings, cargo, ropes, chairs — but also bodies.

The ship turned upside down as it sank, so "just imagine a room that is flipped," said Hwang, who doesn't participate in dives himself but is closely involved in every other part of the operation. "Everything is floating around, and it's hard to know exactly where they are."

It is a delicate operation. Divers must move quickly to find decomposing corpses, but they must also be cautious to protect themselves from injury and keep their air supply hoses from getting cut off. The divers can often work for about an hour when they're hooked up to the hoses, Hwang said.

Some divers use oxygen tanks, but that typically allows for only about 20 minutes under water.

As they explore the hallways of the ship, bodies in lifejackets often float above them, near what used to be the floor, and divers must reach up to grab the bodies and pull them close so they can hold them while notifying colleagues above. They then carefully push the body through an open window cleared of broken glass and debris and let it float up to the boats.

Hwang says divers take special care with decaying bodies to make sure they don't damage them further. When a body without a life jacket is found one diver wraps his arms around the body and another diver pulls his colleague and the body to the surface with a rope.

The work is dangerous.

Air supply problems recently forced two members of Hwang's team to make risky, rapid ascents from about 30 meters (120 meters) underwater to the surface. Rising too quickly puts divers at risk of decompression sickness, also known as the bends, which in severe cases can be fatal. The two divers, he said, were treated in decompression chambers. They're now resting, with one suffering from back pain.

It's also emotionally exhausting, and divers often find themselves thinking of the lives lost.

Hwang said his divers try to avoid looking at the eyes of the bodies they retrieve to minimize the shock. It's not always possible. "Even though they have a lot of diving experience, they get really frightened when they first face the bodies," he said.

Many of the students are found hugging each other.

"How hard it must have been for the kids, with the cold water rushing in and darkness coming over them," Hwang said. "Yesterday, I had a lump in my throat talking about this. I thought to myself: Why did I tell them that I can help with rescues and have a lot of experience when I can't even save one life here?"