There is still no official explanation for the sinking, although the government has launched a formal inquiry.
The ship, built in Japan 20 years ago, was following a well travelled route.
Although the wider area has rock hazards and shallow waters, they were not in the immediate vicinity of its usual path.
The vessel, carrying 475 passengers and crew, capsized on Wednesday during a short journey from the port of Incheon to the holiday island of Jeju.
Chonghaejin Marine Co Ltd, based in Incheon, issued a brief statement via local media apologising for the accident but has made no further comment.
The ferry has a capacity of about 900 people and an overall length of 146 metres (480 feet).
Shipping records show it was built in Japan in 1994. It has been reported that the Chonghaejin Marine Co Ltd became the owner of the vessel in October, 2012, according to the Mirror.