Abstract: A method of providing a habitable dry work chamber for conducting work on an underwater work surface when the nature of the work is such that dangerous fumes and gases are produced. An underwater gas pocket work unit is attached to the underwater work surface to define a work chamber that may be entered from beneath through the water. The work unit includes a structure consisting of walls defining a work opening, which, when positioned with the work opening at the work surface, defines a work chamber that is accessible only from beneath. The structure is sealed at the work opening to the work surface to define the work chamber, wherein the work chamber is defined solely by the structure and the work surface. A habitable gas that is heavier than the dangerous fumes and gases is caused to flow continuously into the work chamber through a valve in the structure to provide a gaseous pocket in the upper portion of the work chamber when the structure is sealed to the underwater work surface.

Abstract: A universal apparatus for quickly and safely sealing the external opening between a propeller shaft and a stern tube on a ship on which the stern tube has a lower portion which terminates in an aft face that is approximately perpendicular to the tube's longitudinal axis and an upper portion which extends further aft. The apparatus includes a rigid housing for generally covering said external opening; closure means coupled to the housing for creating a seal between the housing and the shaft and between the housing and the lower portion of the tube; and a mechanical expansion assembly for creating a seal between the housing and the extended upper portion of the tube.

Abstract: An underwater air pocket work unit has a work chamber contained within a double walled flotation chamber, the upper end of which has a resilient gasket to seal against the hull of a vessel, or other submerged structure. The work chamber is open completely through the structure to provide unobstructed access at both ends and the flotation chamber is open at the lower end. Valves are provided for admitting pressurized air to the flotation chamber to control the buoyancy for holding the structure in place, and for admitting air to the work chamber as necessary for working space. Both chambers have dump valves for releasing the air and the work chamber has window ports for holding work lights.

Abstract: A cofferdam for closing off underwater openings in ships' hulls and the like includes a box-like structure having a flat wall of a size and configuration for covering a ship's openings, with peripheral walls for extending around the flat wall and around the opening for sealingly engaging the ship's hull and defining a chamber around the opening. Conduits are provided for communication with a pump for pumping fluid or water from the chamber of the cofferdam and for venting the dam either to atmosphere or the water for filling the cavity. Fastenings include J-bolts in one configuration for securing the cofferdam to grill work and the like inside a opening to a sea chest, and a hogging type rigging in another embodiment for securing where grill work and the like is not available. The cofferdam is constructed of wood for providing buoyancy in water and includes reinforcing bars extending across the face of the dam which are in the form of closed box beams for providing additional buoyancy.