Semi-Submersible Rig
Semisubmersible rig is a floating offshore drilling unit. As the name suggest, semisubmersible rig is partially submerged into water. The rig floats on hollow steel cross sections called "Pontoons". Since the rig doesn't float on water surface, it provides more stable platform for drilling as compared to a drillship. Semisubmersible rigs are used for drilling well in 1,000 feet to 3,500 feet water depth.