Abstract: A subsea caisson or silo for housing wellhead equipment and methods of installing it is disclosed. A caisson which is sized to receive equipment that is to remain subsea has a closed top and open bottom. The caisson is lowered to the seabed and hydrostatic pressure in combination with a suction jet is used to remove the internal soil. If required the caisson may include a conical suction head located near the bottom of the caisson wall and rotatable cutting heads are fixed to its lower surface so as to cut into sea bottom material of hard consistency.