Almost three years ago, the ferry Sewol sank in rough seas off South Korea. More than 300 people perished, mostly high school students on a field trip.Now, South Korea's government is trying to raise what's left of the 6,800-ton ship. As NPR's Elise Hu reports from Seoul, nine of the people who were aboard that day in April 2014 remain missing, and families hope to recover those bodies once the Sewol has been lifted out of the water and put in dry dock.Dozens of divers are involved in the salvage operation, Elise says.Crews had the ship partway out of the water when their efforts hit what could be a significant snag.An official from the Ministry of Oceans and Fisheries, Lee Cheoljo, told reporters that workers have discovered that a vehicle ramp is dangling from the Sewol's left side, according to The Associated Press. Until the ramp is cut away, crews can't load the ferry onto the semi-submersible heavy-lift vessel that would carry it into port. Cheoljo said divers will need to remove the ramp using welding equipment, and that it's vital to finish the work in enough time for the ferry to be loaded by midnight Friday.The mission is up against impending weather — currents are expected to strengthen on Saturday. Workers had hoped to finish the job Thursday morning, but they hit an earlier snag when the Sewol began rubbing against the pulleys and equipment on the barges lifting it, requiring the workers to rebalance it.Some family members of the dead and missing watched the crews try to raise the ship. The Associated Press reports that some cried as they watched the wreckage through telescopes: