A fleet of yellow, stingray-shaped robot submarines will monitor the most delicate and complex operation in the Costa Concordia refloating -- raising the wrecked cruise liner by another 40 feet and towing it away.

Measuring only 12 inches wide and weighing just 13 pounds, the VideoRay Pro 4 remotely operated vehicles (ROVs) play a crucial role in the largest maritime salvage operation ever. They're used in every underwater activity around the stricken ship.

Over the past two and half years, these “swimming cameras” have recorded 45,000 hours of video footage, making this the most intensive use of underwater ROVs in the history of salvage.

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“On this job our ROVs worked 24 hours a day. There were more hours logged on this project than any other VideoRay job ever,” Scott Bentley, VideoRay's president, told Discovery News.

The company, located in Pottstown, Penn., is the largest producer of ROVs in the world. Among various missions, their miniature ROVs carried under-ice investigation in Antarctica and Cenote exploration in the Yucatan for Mayan artifacts.

They also penetrated for the first time the USS Arizona in Pearl Harbor, and explored the RMS Lusitania off the Irish coast, capturing images unseen since the ship’s sinking in 1917.

In Giglio, VideoRays have surveyed and inspected the entire 950-foot-long and 115-foot-wide Concordia, playing a major role from the initial search for the victims through the complex final stage which is leading to the wreck removal from the Tuscan island.

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“VideoRay ROVs were used to keep divers safer by observing their work and going into confined spaces so that divers didn’t have to,” Bentley said.

The yellow submarine robots  are small enough to penetrate areas of shipwrecks inaccessible to larger ROVs. They can be used in extreme situations such as rough seas, strong currents up to 4 knots, and can sustain temperatures from 32 to 122 degrees F for hours, while diving down to 1,000 feet.

Ultra-portable and completely computer driven, the tethered units feature two thrusters in the back which turn and push them forward, while on the top, a propeller allows the robot submarines to go up and down. The front is equipped with two powerful LED lights and a high-resolution camera to transmit underwater images.

VideoRays send images to the control room aboard the Concordia. The Parbuckling Project

“A sonar can be placed underneath, but in Giglio they did not need it since the water is so clear,” Bentley said.

Among various tasks, these ROVs entered the Concordia's dangerous engine room, established the condition of pollution at each level of the ship, and explored the rusting hull inch by inch.

“They minimized risk to divers during the salvage operation in challenging conditions,” Bentley said.

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Every day since the beginning of the removal project,  VideoRays have been starting their mission by going to the exact underwater location where a job has to be done. The diver then follows the tether. When he reaches the spot, the ROV lights can be turned up to illuminate the scene.

“The diver supervisor has two views, one is the helmet camera worn by the diver, the other is the view from the VideoRay. This is useful as the supervisor gets a wider view and can tell the diver where to go,” Bentley said.

During the full refloating and the following towing operation, all VideoRays will be active monitoring the underwater condition.

Until last week, technicians from Titan, the marine salvage company in charge of the Costa Concordia project, could rely on a fleet of seven VideoRay ROVs.

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On Monday, during the first day of the refloating operations, one was lost beneath the ship.

“It was a $25,000 investment, but if a diver had been hurt or killed it would have been much worse,” Bentley said.

VideoRay ROVs will possibly continue to work on Giglio even after the wreck is removed. They will be employed in the search for the last victim, whose remains have never been found, and will monitor the cleaning operations which will follow the Costa Concordia removal.