Story highlights Rescuers describe finding 48 girls in one room meant for 30 people

Divers trying to reach room where another 50 girls believed to have been, commander says

Search effort now expected to slow, says commander of the rescue operation

Prosecutors investigate Sewol's sister ship, find numerous safety problems

In the final, chaotic moments before the South Korean ferry Sewol rolled over and sank into the chilly waters of the Yellow Sea, 48 girls obeyed the orders of crew members and put on their life vests.

Perhaps afraid, they all crammed into a single room meant for 30.

None of them survived.

The account of the recovery of the girls' bodies, offered Friday by rescue officials, offers a glimpse of the final moments aboard the sinking ferry, which went down on April 16 with 476 people aboard.

It also illuminates the daunting task facing divers trying to retrieve bodies while maintaining a fading glimmer of hope that perhaps, somewhere aboard the ferry, someone remains alive.

Rescue officials spoke of a forest of floating objects, doors forced shut by enormous water pressure, and of currents that tug at the breathing tubes that keep them alive as they look for the dead.

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Photos: Photos: South Korean ferry sinks – A relative of a victim weeps as she and others stand on the deck of a boat during a visit to the site of the sunken Sewol ferry on April 15, 2015 -- one day before the one year anniversary of the disaster. Hide Caption 1 of 55 Photos: South Korean ferry sinks – A relative hands out flowers to others on the deck of a boat during a visit to the site of the sunken ferry. More than 100 relatives of victims of South Korea's Sewol ferry disaster tearfully cast flowers into the sea. Hide Caption 2 of 55 Photos: South Korean ferry sinks – A man hold a flower as he stands on the deck of a boat during a visit to the site of the sunken Sewol ferry, off the coast of South Korea's southern island of Jindo. Hide Caption 3 of 55 Photos: South Korean ferry sinks – The mother of Sewol ferry disaster victim, Danwon High School student Lim Kyung-Bin, attends a rally to pay tribute to the victims of the ferry disaster on April 11, 2015, Seoul, South Korea. Hide Caption 4 of 55 Photos: South Korean ferry sinks – Relatives of victims of the Sewol ferry disaster march across a bridge over the Han river in Seoul on April 5, 2015. More than 200 people participated in the march from Ansan city. Many of them were the parents of the 250 students who died when the overloaded ferry sank off Jindo on April 16, 2014. Hide Caption 5 of 55 Photos: South Korean ferry sinks – Relatives of victims of the Sewol ferry hold portraits of victims during a rally on April 5, 2015 in Seoul. Relatives, students and citizens attended the vigil to pay tribute to the victims of the ferry disaster and demanded that the wreckage be salvaged. Hide Caption 6 of 55 Photos: South Korean ferry sinks – Sewol ferry captain Lee Joon-Seok was acquitted of murder, avoiding a death sentence, but was sentenced to 36 years in jail on November 11 for his role in the maritime disaster that killed more than 300. Hide Caption 7 of 55 Photos: South Korean ferry sinks – Shoes believed to belong to the missing and the deceased are on display at the harbor. Hide Caption 8 of 55 Photos: South Korean ferry sinks – Jindo harbor, where the search operation is based, has become a memorial for those who lost their lives. Yellow ribbons and photos are displayed as people come to pay their respects. Hide Caption 9 of 55 Photos: South Korean ferry sinks – A joint government-civilian task force is still looking for the missing, but winter is fast approaching. Hide Caption 10 of 55 Photos: South Korean ferry sinks – Ten are still missing from tragic ferry sinking last April, which killed more than 300. Six months later, families are still waiting for their loved ones to be found. The parents of 16-year-old Huh Da-yoon, pictured, are among them. Hide Caption 11 of 55 Photos: South Korean ferry sinks – The families of the ten who remain missing have been waiting in Jindo Indoor Gymnasium since the first day. Families can watch search mission in real time on a large monitor in the gym. Hide Caption 12 of 55 Photos: South Korean ferry sinks – South Korean President Park Geun-hye weeps while delivering a speech to the nation about the sunken ferry Sewol at the presidential Blue House in Seoul, South Korea, on Monday, May 19. More than 200 bodies have been found and nearly 100 people remain missing after the ferry sank April 16 off South Korea's southwest coast. Hide Caption 13 of 55 Photos: South Korean ferry sinks – Police in Seoul detain a protester during a march Saturday, May 17, for victims of the Sewol. Hide Caption 14 of 55 Photos: South Korean ferry sinks – A girl in Seoul holds a candle during a service paying tribute to the victims of the Sewol on Wednesday, April 30. Hide Caption 15 of 55 Photos: South Korean ferry sinks – People pay tribute to victims at a memorial altar in Ansan, South Korea, on Tuesday, April 29. Hide Caption 16 of 55 Photos: South Korean ferry sinks – A police officer holds an umbrella for a relative of a missing ferry passenger Monday, April 28, in Jindo, South Korea. Hide Caption 17 of 55 Photos: South Korean ferry sinks – South Korean Buddhists carry lanterns in a parade in Seoul on Saturday, April 26, to honor the memory of the dead and the safe return of the missing. Hide Caption 18 of 55 Photos: South Korean ferry sinks – Divers search for people in the waters near Jindo on April 26. Hide Caption 19 of 55 Photos: South Korean ferry sinks – People in Ansan attend a memorial for the victims on April 26. Hide Caption 20 of 55 Photos: South Korean ferry sinks – A diver jumps into the sea near the sunken ferry on Friday, April 25. Hide Caption 21 of 55 Photos: South Korean ferry sinks – A relative of a passenger weeps while waiting for news of his missing loved one at a port in Jindo on April 25. Hide Caption 22 of 55 Photos: South Korean ferry sinks – People attend a memorial for the victims at the Olympic Memorial Hall in Ansan on Thursday, April 24. Hide Caption 23 of 55 Photos: South Korean ferry sinks – Yellow ribbons honoring the victims flap in the wind as a hearse carrying a victim's body leaves Danwon High School in Ansan on April 24. Most of the people on board the ferry were high school students on their way to the resort island of Jeju. Hide Caption 24 of 55 Photos: South Korean ferry sinks – People attend a memorial for the victims at Olympic Memorial Hall in Ansan. Hide Caption 25 of 55 Photos: South Korean ferry sinks – Search personnel dive into the sea on Wednesday, April 23. Hide Caption 26 of 55 Photos: South Korean ferry sinks – Flares light up the search area on Tuesday, April 22. Hide Caption 27 of 55 Photos: South Korean ferry sinks – The sun sets over the site of the sunken ferry on April 22. Hide Caption 28 of 55 Photos: South Korean ferry sinks – A relative of a ferry passenger prays as she waits for news in Jindo on April 22. Hide Caption 29 of 55 Photos: South Korean ferry sinks – The search for victims continues April 22 in the waters of the Yellow Sea. Hide Caption 30 of 55 Photos: South Korean ferry sinks – Rescue workers in Jindo carry the body of a passenger on Monday, April 21. Hide Caption 31 of 55 Photos: South Korean ferry sinks – Divers jump into the water on April 21 to search for passengers near the buoys that mark the site of the sunken ferry. Hide Caption 32 of 55 Photos: South Korean ferry sinks – Search operations continue as flares illuminate the scene near Jindo on Sunday, April 20. Hide Caption 33 of 55 Photos: South Korean ferry sinks – Relatives of missing passengers grieve April 20 in Jindo. Hide Caption 34 of 55 Photos: South Korean ferry sinks – Relatives of passengers look out at the sea from Jindo on April 20. Hide Caption 35 of 55 Photos: South Korean ferry sinks – Police officers in Jindo stand guard Saturday, April 19, to prevent relatives of the ferry's missing passengers from jumping in the water. Some relatives said they will swim to the shipwreck site and find their missing family members by themselves. Hide Caption 36 of 55 Photos: South Korean ferry sinks – Family members of missing passengers hug as they await news of their missing relatives at Jindo Gymnasium on April 19. Hide Caption 37 of 55 Photos: South Korean ferry sinks – South Korean Navy Ship Salvage Unit members prepare to salvage the sunken ferry and search for missing people on April 19. Hide Caption 38 of 55 Photos: South Korean ferry sinks – Lee Joon Suk, the captain of the Sewol, is escorted to the court that issued his arrest warrant Friday, April 18, in Mokpo, South Korea. Hide Caption 39 of 55 Photos: South Korean ferry sinks – A woman cries as she waits for news on missing passengers April 18 in Jindo. Hide Caption 40 of 55 Photos: South Korean ferry sinks – A searchlight illuminates the capsized ferry on Thursday, April 17. Hide Caption 41 of 55 Photos: South Korean ferry sinks – A woman cries during a candlelight vigil at Danwon High School in Ansan, South Korea, on April 17. Hide Caption 42 of 55 Photos: South Korean ferry sinks – Family members of passengers aboard the sunken ferry gather at a gymnasium in Jindo on April 17. Hide Caption 43 of 55 Photos: South Korean ferry sinks – The body of a victim is moved at a hospital in Mokpo on April 17. Hide Caption 44 of 55 Photos: South Korean ferry sinks – Relatives of a passenger cry at a port in Jindo on April 17 as they wait for news on the rescue operation. Hide Caption 45 of 55 Photos: South Korean ferry sinks – South Korean coast guard members and rescue teams search for passengers at the site of the sunken ferry on April 17. Hide Caption 46 of 55 Photos: South Korean ferry sinks – A relative of a passenger cries as she waits for news on Wednesday, April 16. Hide Caption 47 of 55 Photos: South Korean ferry sinks – Relatives check a list of survivors April 16 in Jindo. Hide Caption 48 of 55 Photos: South Korean ferry sinks – Rescue crews attempt to save passengers from the ferry on April 16. Hide Caption 49 of 55 Photos: South Korean ferry sinks – A relative waits for a missing loved one at the port in Jindo. Hide Caption 50 of 55 Photos: South Korean ferry sinks – Parents at Danwon High School search for names of their children among the list of survivors. Ansan is a suburb of Seoul, the South Korean capital. Hide Caption 51 of 55 Photos: South Korean ferry sinks – Helicopters hover over the ferry as rescue operations continue April 16. Hide Caption 52 of 55 Photos: South Korean ferry sinks – Officials escort rescued passengers April 16 in Jindo. Hide Caption 53 of 55 Photos: South Korean ferry sinks – A passenger is helped onto a rescue boat on April 16. Hide Caption 54 of 55 Photos: South Korean ferry sinks – A passenger is rescued from the sinking ship on April 16. Hide Caption 55 of 55

Civilian diver Chun Kwan-geung, one of the many rescuers working in the murky waters, spoke of having to break out windows to get to the lower decks of the ship, which now lies on its right side on the seafloor some 73 meters (240 feet) below the surface.

"The rescue effort is getting slower," said South Korean navy Capt. Kim Jin-hwang, commander of the rescue operation. "The divers already searched all the places easily accessible. They are expecting the search to become harder because of increasing currents and harsher weather. But the navy will not stop until the last body is found."

As if highlighting the point, Kim's divers are trying to find their way into another dormitory-style room where 50 girls were believed to be as the ship began to sink.

So far, rescuers have retrieved 187 bodies. Another 115 people remain missing, although no one has been rescued since 174 were plucked from ship and sea the day the ferry sank.

As the effort inside the ship continues, South Korean authorities are pressing a criminal investigation into the sinking. It's resulted in the arrests of the ship's captain and 14 other members, searches of the company that owned the ferry and the home of the man whose family controls it , and a wide-ranging probe into the country's marine industry.

Safety concerns about sister ship

Prosecutors in Mopko, South Korea, who are leading the ferry investigation told CNN's Nic Robertson on Friday that authorities have yet to determine what caused the sinking.

Leading theories include changes made to increase the ferry's passenger capacity and shifting cargo.

On Friday, investigators checked out the Sewol's sister ship, the Ohamana, and said they found 40 of its life rafts weren't working, emergency slides to help evacuate passengers were inoperable, and equipment to tie down cars and cargo either was nonexistent or didn't work very well.

Like the Sewol, the Ohamana had been modified to add more passengers, the prosecutor's office said.

The ship arrived in Incheon on April 16, the same day the Sewol sank, and has not left yet, officials said.

Investigators are looking into whether those modifications could have contributed to the Sewol's fate.

Kim Yong-rok, an opposition lawmaker who represents Jindo, an island near where the ship sank, told CNN that modifications to add 117 more passenger cabins to the ship raised the ferry's center of gravity.

On Friday, the South Korean Ministry of Oceans and Fisheries announced it would ask lawmakers to consider legislation prohibiting modifications to ships to increase passenger capacity.

Government investigators are also probing the private organization that conducts ship safety inspections on behalf of the government to determine if any wrongdoing was involved in the certification of the Sewol after its 2013 modifications.

Families confront officials

The revelations about the sister ship came the day after angry relatives of missing ferry passengers cursed government and police officials for failing to do enough to save the lives of their loved ones as hopes of finding survivors dimmed.

The relatives berated Fisheries Minister Lee Ju-young and two coast guard officials, accusing them of misleading the public about the operation and of wasting time.

"How can you fool us into believing you were out there trying to save our children?" one mother yelled at the officials.

Also, officials at the South Korean headquarters for the task force coordinating the search told CNN that they believe the body of a boy who reportedly made the first emergency call from the ship after it began to list sharply has been recovered. DNA tests will help officially identify the remains, officials said early Friday.

Also on Friday, an official involved in the investigation in Mokpo asked for patience.

"I know a lot of people are curious as to the cause of the accident, but we don't have the information yet," said Heo Yong-beom, a maritime safety judge. "We will try our best to satisfy and answer questions."

'We join you in mourning'

Meanwhile, U.S. President Barack Obama, in South Korea for a previously scheduled trip, presented South Korean President Park Geun-hye with an American flag that flew over the White House the day the ferry sank.

"I'm very mindful that my visit comes at a time of mourning for the people of this nation," he told the U.S. and the South Korean delegations. "As allies but also friends, we join you in mourning the missing, and especially the young people."

The delegations held a moment of silence, then Park thanked Obama for the gesture.

"The Korean people draw great strength from your kindness," she said.