Rescuers searching for bodies have been able to take advantage of better weather on Tuesday, officials say, with more than 190 passengers still missing or presumed trapped inside the vessel.
The ferry tipped over and sank within two hours, but it is not yet clear why.
The crew have been criticised for allegedly failing to save passengers.
Five have been charged with not fulfilling their duty to evacuate passengers safely, officials told the South Korean Yonhap news agency.
At least six other crew members are reported to have been detained.
As the ship listed passengers were told to remain in rooms and cabins, reports suggest, amid confusion on the bridge over whether to order them to abandon ship.
The first distress call from the sinking ferry was made by a boy with a shaking voice, officials told Reuters.
It reported that his plea for help was followed by about 20 other emergency calls from children on board the ship.
Many family members and friends of those on board the ferry are still awaiting news of the fate of their loved ones 
Teams of divers have been searching the sunken ferry for the bodies of those who died 
Bodies are being brought to shore - where many relatives wait for news of their loved ones A crew member quoted by local media said that attempts to launch lifeboats were unsuccessful because of the tilt of the ship. Only two of the vessel's 46 lifeboats were reported to have been deployed.
South Korean President Park Geun-hye on Monday condemned the conduct of some of the crew, calling it "akin to murder".
The BBC's Jonathan Head in nearby Jindo island says that the rescue operation has now become something of a grim routine, with police boats regularly returning from the scene of the disaster with bodies recovered by military divers.
Our correspondent says that most of the families of those still missing have accepted that no more survivors will be found.
Robot readyA total of 174 passengers were rescued from the Sewol, which capsized as it sailed from Incheon in the north-west to the southern island of Jeju.
But there were 476 people on board, including 339 children and teachers on a school trip. Many were trapped inside the ship as it listed to one side and then sank.
Divers have managed to reach many of the cabins in the hull of the upturned ferry, although they are still trying to get into the ship's restaurant, where they believe many of the passengers were trapped.
They have also loaded an underwater robot at the port this morning, ready to help in the operation to bring the hull to the surface.
Crabster robot 
The crabster robot is the size and weight of a Smart carIt is designed to work up to 200m below the surface in high tidal currents where divers are unable to operate A 500m-long cable allows four operators to control the robot from a surface vessel. Data is also fed to the surface via the cableIt is equipped with 10 optical cameras and a long-range scanning sonar Rescue officials say they will keep searching with divers for another two days, but that the families of the victims have agreed that the salvage operation can begin after that.
Investigations are focusing on whether the ferry took too sharp a turn - perhaps destabilising the vessel - before it started listing and whether an earlier evacuation order could have saved lives.
Captain Lee Joon-seok was not on the bridge when the ferry began listing. It was being steered by a third mate who had never navigated the waters where the accident occurred, prosecutors say.
The captain and two other crew members have been charged with negligence of duty and violation of maritime law. Four more crew members were reported to have been detained on Monday and two on Tuesday.
There were up to 30 crew members on the stricken ship, reports say, and some seven of them are missing.
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