alexander the great one of the first to use bell diving 16th century used to find things sunken or lost over overboard at depths man can not swim.(people only survived under 10 meters). deepest reached 80 meters.  

  

used by fisher men and commercial divers made it easy 

to catch fish and find sunken items. 18th century (30-35 meters max).   

 

  

 this was one of the first commercial diving bells air was pumped down to the bell with the workers in side this was a dead mans job little money and little chance of survival. start of the 19th century.   

 

military was one of the first to make a successful under water breathing unit 

in the 21st century the rebreather was invented and is widely used in the world by many skilled scuba divers and the digital mask that tells u depth and air pressure puting a computer in a mask is not the best i dear because it is usaly the most lost item in scuba diving