Semisubmersible drilling rig:A floating offshore drilling unit that has pontoons and columns that when flooded cause the unit to submerge in the water to a predetermined depth.
Living quarters, storage space, and so forth a reassembled on the deck.
Semisubmersible rigs are either self-propelled or towed to a drilling site and either anchored or dynamically positioned over the site, or both.
In shallow water, some semisubmersibles can be ballasted to rest on the seabed.
Semisubmersibles are more stable than drill ships and ship-shaped barges and are used extensively to drill wildcat wells in rough waters such as the north sea.
Two types of semisubmersible rigs are the bottle-type semisubmersible and the column-stabilized semisubmersible.
See floating offshore drilling rig.