The rig is held down by 12 mooring lines that are anchored in the sea floor. The platform of the rig sits on a column that is balanced by chambers of air and sea water. The DDCV rigs are the least harmful to the environment because of the lack of disturbance to the sea floor. (yes there are 12 moor line anchors but compare that to four to eight huge pillars that are sunk into the sea floor). These are the only rigs, along with the drill ships that are not completely anchored to the sea floor.
