Published : 2014-04-26 14:19
Updated : 2014-04-27 09:53
Frogmen have battled strong currents, poor visibility and blockages caused by floating furniture as they have tried to get inside the upturned vessel, which rests on a silty seabed.
The challenging conditions have meant divers are unable to spend more than a few minutes in the ship each time they go down.
Even so, they are coming across horrifying scenes in the murky water, including one dormitory room -- which would normally have held around 31 people -- packed with the bodies of 48 students wearing lifejackets.
Around a quarter of the 187 dead recovered so far have been found in waters outside the sunken vessel, and there are fears that some of the missing may have drifted free from the wreck.
That could be exacerbated if the sea is churned by the gathering storm, scattering bodies.
Authorities -- wary of the palpable anger among relatives -- have mobilised trawlers and installed 13-kilometre (eight-mile)-long nets anchored to the seabed across the Maenggol sea channel to prevent the dead being swept into the open ocean.
Dozens of other vessels and helicopters have been scouring the site and beyond, with the search operation expanded up to 60 kilometres (40 miles) from the scene of the disaster.
Police and local government officials will also be mobilised to scour coastal areas and nearby islands, a coastguard official said.
Furious families demanded a meeting with Choi Sang-Hwan, deputy head of the Korea Coastguard, near the pier in Jindo Port, urging him to send the divers back into the water.
"We are waiting for the right moment as conditions in the sea are not favourable," said Choi.
It took divers working in difficult and dangerous conditions more than two days to get into the sunken ferry and two more days to retrieve the first bodies.
Many relatives believe some of the victims may have survived for several days in trapped air pockets, but perished in the cold water after no rescue came.
As a result some have asked for autopsies to be performed, to see if it would be possible to determine the precise cause and time of death.
On Saturday, a US navy rescue and salvage vessel, the USS Safeguard, arrived at Jindo, AFP journalists on the scene said.
The vessel has "divers and other necessary equipment aboard, but it remains to be seen how the ship can contribute to the ongoing efforts to retrieve bodies", a US military spokesman told AFP.
The Sewol's captain, Lee Joon-Seok, and 10 crew members have been arrested on charges ranging from criminal negligence to abandoning passengers.
The captain has been sharply criticised for delaying the evacuation order until the ferry was listing so badly that escape was almost impossible.
Prosecutors have raided a host of businesses affiliated with the ferry operator, the Chonghaejin Marine Company, as part of an overall probe into corrupt management.
The widening investigation has also seen travel bans put on eight current and former executives of the Korea Register of Shipping -- the body responsible for issuing marine safety certificates. (AFP)