Instrument: Self-Contained Underwater Breathing Apparatus

The self-contained underwater breathing apparatus or scuba diving system is the result of technological developments and innovations that began almost 300 years ago. Scuba diving is the most extensively used system for breathing underwater by recreational divers throughout the world and in various forms is also widely used to perform underwater work for military, scientific, and commercial purposes.

Reference: http://oceanexplorer.noaa.gov/technology/diving/diving.html