While earlier inventors had developed designs to help people breathe underwater, Leonardo enhanced the design to a more functional and practical format. Leonardo thought this diving suit would enable men to repair the hulls of ships underwater, or in fact permit an army of men in SCUBA to march underwater to attack the hulls of enemy ships undetected. In a second design, air tubes descending from a bell-shaped floating buoy at the surface are attached to a face mask. A diving suit based on this design using pig leather, bamboo tubes and a cork float was tested by diver Jacquie Cozens in 2002 – with limited success.