Story highlights Parents of the victims share their grief as vessel returns to surface

The Sewol ferry sank on April 16, 2014, killing 304 people on board

Efforts to raise it have been underway ever since, amid frequent delays

(CNN) Three years after they watched in horror as a passenger ferry carrying their children sank off the coast of South Korea, parents of the victims watched the vessel return to the surface Thursday.

"I feel so sorry for my child, thinking how he suffered, I wasn't there to offer him anything," Lim Young-jae, who lost his son in the Sewol ferry disaster, told CNN.

The Sewol sank on April 16, 2014, killing 304 people -- mostly teens on a school trip. Nine bodies are still missing; it is hoped they will be recovered once the vessel is out of the water.

One of the first images of the Sewol ferry as it emerges after three years underwater.

Jang Dong-won voiced the frustration many of the victims' parents feel that the salvage operations have taken this long.

"It's the first time in three years I've seen the ferry with my naked eye, and it's hard to understand why we couldn't lift it before," he said.

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