"I was preparing to report for duty when there was a sound of an explosion which hurt my ears and I was thrown in the air," said Oh Seung-tak, a senior petty officer.
"Power was immediately cut. I was hit in the face by a flying computer and lost consciousness momentarily. When I regained my senses, everything was dark."
Oh, who was in charge of munitions storage, said that he detected no smell of explosives from inside the ship and nothing unusual before the blast.
|Rescue teams have said the salvage of vessel parts could take weeks [Reuters]
US and South Korean teams are preparing to lift the shattered hull sections of the Cheonan from the bed of the Yellow Sea in search of clues to the disaster which left 46 sailors dead.
However experts say the salvage operation could take several weeks.
The ship is thought to have broken into at least two pieces, leading to suggestions that it was torn apart either by a torpedo or a mine.
The disputed border area was the scene of deadly naval clashes between North and South Korea in 1999 and 2002 and a firefight last November.
Captain Choi Won-il said that his fellow officers at the time reported the blast "seemed to be a shock from outside".
Choi was trapped in his cabin until crewmen broke it open, and climbed a fire hose to reach the deck.
The disaster has sparked intense public speculation and a series of conspiracy theories on the internet, including a suggestion that the warship hit an underwater obstacle and tore itself apart.
But Kim Byong-nam, a survivor from the ship, appeared to discount that possibility.
"If a ship hits a rock or a sandbank, it would basically make a tearing sound," he said.
North Korea has made no mention of the sinking and Lee Myung-bak, the South Korean president, has cautioned against premature speculation over the cause.