These difficulties were fully considered and plans made for overcoming them. As it was an impossibility to increase the depth of the dry dock, the only way to solve this problem was to decrease the depth of water that the battleship would draw. The engineer accordingly proposed to detach the funnels, gun-turrets and other top hamper from the deck of the vessel. So firmly embedded were these things in the mud, that the feat of cutting them off appeared to be more than mortal man could accomplish. It was, too, pointed out that if divers tried to clear the mud away from round the funnels, to enable them to work at their task, the sea would quickly fill up the cavities again. Yet another aspect of the problem was that the mud pressing upwards against the deck of the battleship was preventing her from sinking deeper, and if the mud were removed the whole weight of the _Leonardo da Vinci_ would once more rest on her funnels and turrets and drive them deeper still into the clay. But the engineer, with a stroke of genius, made no attempt to clear away the mud at all. Instead, he tackled the job from inside the ship. Certain compartments were pumped out and used as air-locks, and in one turret the salvors succeeded, by the use of compressed air, in lowering the water to a level of 56 feet below the surface of the sea. The men who performed the mighty task of detaching the turrets from the ship actually worked 20 feet below the level of the mud. All around them outside was 20 feet of thick black ooze, and above that the illimitable ocean; yet the air we breathe, properly compressed, held back the deadly waters and enabled the men to work in safety. No wonder the experts say we are only just beginning to discover the remarkable power of compressed air as an aid to salving ships! Throughout 1918, some 150 men laboured about the ship to free her from her top hamper and masts. Despite all difficulties, the gun-turrets, funnels and other deck projections were detached from the ship and specially prepared so that when the vessel was raised they, too, could be brought to the surface. The open spaces in the deck left by funnels and turrets were covered in and made quite watertight, scores of tons of cork being packed into the _Leonardo da Vinci_ to give her buoyancy.