Abstract: A housing chamber for use in underwater arc welding is constructed in the form of a portable hollow cylinder open at one end and having a side opening in which is movably mounted a welding gun for effecting a welding operation on a workpiece through the open end. The interior of the housing chamber is illuminated and a viewing plate slanted relative to the axis of the cylinder closes the other end. The chamber is provided with means for introducing gas under pressure to purge the chamber of water. An L-shaped vent tube adjacent the viewing facilitates purging the housing chamber of water. The vent tube is rotatably adjustable relative to the housing chamber to control the amount of gas discharged. A porous rubber gasket member is provided between the workpiece and the open end of the cylinder to permit escape of gas therethrough to facilitate relative movement between the cylinder and the workpiece.