Hydraulic thrusters and acoustic beacons

Second day on the ship and I have already learned new terms that relate to the ship and what will happen once we set sail tomorrow at 16:00 ship time. One of the questions I had about drilling from a ship is how does the ship stay above the drill hole? I knew there had to be some way to stabilize the ship so that during the drilling process the drills and the cores would not break or snap but I wasn't quite sure exactly if it was a set of anchors or legs that extended down from the ship to the sea floor. 

A set of 12 hydraulic thrusters will drop down into the water just below the boat that will stabilize the ship when we reach our drilling location. These hydraulic thrusters that arc controlled by a computer system up on the bridge will act as propellers that will rotate to steer the ship in the swells and keep the boat within a range that is safe for drilling. 

How will the boat know what the safe floating range is for drilling? The ship today uses both GPS and acoustic beacons. Before GPS, the boat relied on the beacons to tell the location of the shop based on the location over the hole. Today both of these technologies are used together. The GPS can provide a pretty accurate location of the boat, but then the beacons that are dropped to the sea floor are used to help keep the boat within that margin of error that is still present when using GPS. They also use the beacons incase the GPS signal goes out.  When drilling with this expensive equipment, it's better to be on the safe side and not rely on just one technology.