This combination consists of a tube which may be built of any desired length or so constructed that this may be increased by the insertion of additional sections. This tube is provided with an operating compartment or working chamber at the free end, and water-ballast tanks are distributed throughout the length of the tube so that the structure can be placed in equilibrium with the water when ready for submergence. In the working chamber there are also water-ballast tanks by which that end of the tube can be sunk and caused to rest upon the bottom with any desired pressure or dead weight. This operating chamber has a hatch and door located in its bottom. This bottom door can be opened when needed--the whole compartment becoming then a virtual diving bell, so that divers can be sent out if so wished, or operations through this open passage to the water-bed can be pursued by means of tools and appliances controlled from within the compartment. There is also an air-lock or equalizing chamber. Its purpose is to enable the operators to become gradually accustomed to change of pressure when entering or when leaving the working chamber when the latter is being used with the bottom door open; the air pressure within the compartment would be maintained in constant accord with the water pressure corresponding to the particular depth at which this tube would be in use. The tube itself may have its upper end attached to the side of a surface craft, but preferably it floats in the well of a craft especially designed to work in combination with it, as shown. [Illustration: SEMI-SUBMERGIBLE WRECKING APPARATUS The submergible tube has the diver's operating compartment shut off from the rest of the apparatus by means of an air lock which permits passage from the surface vessel and normal air pressure to the diver's compartment, where the air is under pressure equal to the compartment's depth of submergence, when the diver's exit door is open. The above illustration shows divers "breaking" the cargo out of the hold of a sunken ship and sending it to the surface.] The general method of operating upon a submerged wreck is as follows: The vessel carrying the tube is brought to the place of operation; it may be carried there either by towing or by its own power. The carrying vessel is moored over the wreck by quartering lines; anchor lines connect with anchors run out abeam on each side of the vessel. These lines are controlled from within the operating chamber, when once the anchors are planted, so that the lower end of the tube, when submerged, may be swung through the arc of a circle within the pivotal point at the buoyant end attached to the surface vessel. The operating chamber and tube are lighted electrically, and electricity also supplies power control within the chamber. Compressed air is led into this compartment to supply the chamber when operating under pressure and also to supply any divers sent out therefrom at such times.