||Inventors as early as the 17th Century sought means whereby divers could stay underwater for extended periods. At that time, various types of diving dress and underwater armor attempted to supply fresh air through a surface pipe kept above the water by a float. Air was pumped to the helmet through a pipe from the surface—air pressure serving to keep the water level below the diver's head and the air finally escaping through open vents at the bottom of the jacket.
The diver had to maintain a generally upright position; a fall could result in drowning because the air in the suit was likely to rush out through the vents. To correct this difficulty, the closed type of diving suit was later developed , with improvements, and is still in general use. Instead of the earlier open vents, the closed type of suit had valves that let air out without letting water in, regardless of the diver's position.