Abstract: A composition useful, inter alia, as an insulation material for sealing breaches in architectural barriers, is based on silicone gel which is mixed with powdered lead and lead oxide to achieve desired densities. Silica or silicon dioxide may be utilized to thicken the gel and to maintain the lead and lead oxide in suspension within the gel during curing. The lead acts to increase the density of the gel to enhance the radiation attenuation characteristics of the composition and the lead oxide deters the hardening of the gel in response to radiation.

Abstract: A buoyancy system is disclosed for use in controlling the descent and ascent of an object, such as a pipe line being laid offshore. The system includes a plurality of inflatable, collapsible, submersible buoys which may be remotely controlled by air or other inflating mediums. As each of the buoys, and thus the load connected thereto, is lowered or raised in a body of water the pressure inside the buoys is controlled by a valve which is responsive to the hydro-static pressure in the body of water or the volume of the buoy to maintain a relatively small pressure differential between the pressure inside the buoy and the hydro-static pressure at all depths of submersion whether the amount of buoyancy provided by the buoys is to be positive, negative, or neutral. Also disclosed are a plurality of systems utilizing the submersible buoys of this invention for laying pipe line and other objects on or near the sea bottom.