The Crabster, which began underwater testing in July 2013, can adapt its posture to different current or pressure conditions to a depth of around 200 meters. Using sonar, it scans the landscape for objects of interest, and can relay images through onboard cameras.
The Sewol ferry sinking on April 16, and the South Korean government requested the Crabster's help on April 20. According to Discovery News, while the Crabster was exploring the ocean floor it "found dozens of ships and a swarm of smaller boats surrounding the main rescue barge anchored near the ferry sinking site. Divers were working with a visibility of less than 20 centimeters at a depth of about 45 meters below the surface. They also had to deal with maximum tidal currents of more than 15 kilometers per hour. (Crabster experienced currents of less than 5 kilometers per hour during its initial deployment.)"
"Crabster can stay deeper and longer, and it can see father," explains Bong-Huan Jun, lead researcher at the Korean Institute of Ocean Science and Technology (KIOST), which developed the Crabster. "But Crabster cannot go into the ship. We wanted to work together with human divers, but we had no chance to do."
The Crabster was launched 13 times during the search, spending 15 hours and 36 minutes in the water.
The Crabster team returned to lab on May 20 and unloaded the robot where they joined their fellow citizens in confronting the grim death toll from the Sewol ferry disaster — at least 286 dead, most of them students on a school trip.