South Korea ferry: Was cargo properly secured?
18 April 2014 Last updated at 18:32 BST
A marine salvage consultant with more than 40 years' experience, has speculated on the theories that the ferry which sank off South Korea could have been off course or taken a sudden turn.
Captain John Noble said that had the ship been on its prescribed route, it should not have hit anything on the sea bed as the water should have been deep enough.
"The idea that she did a sudden turn... Had the ship been properly stable when she sailed and the cargo properly secured, that shouldn't have happened.
"If that is what happened, something was deeply wrong when she sailed."
Capt Noble warned that oxygen in air pockets probably would not last very long, but the real issue was the temperature of the water.