Piston pump

This type of pump is in common use as a bilge pump or tank stripping pump. For older vessels steam driven varieties served in almost all systems.
The design is simple, robust and reliable. Materials are very much dependent on the usage but bronze is common for larger parts and stainless steel for piston rods

There are many other forms of positive displacement pump such as rotary vane (often found in use as cooling water pumps, Scroll or Screw pumps were the fluid passes axially along the shaft and Diaphragm Pumps (commonly used as portable salvage pumps) 

This air supply valve assembly normally takes the form of a shuttle valve. source(arab-training.com)