The Sewol, weighing almost 7,000 tonnes, sank on a routine trip from the port of Incheon, near Seoul, to the southern holiday island of Jeju. Investigations are focused on human error and mechanical failure.
The unidentified crew member, speaking briefly to reporters on the way from court back into detention, was speaking behind a surgical mask and wearing a baseball cap with a jacket hood.
More than 300 people, most of them students and teachers from the same school, are dead or missing presumed dead in the April 16 disaster.
As the ferry began sinking, the crew told the children to stay in their cabins.