Underwater diving is going underwater. There are various purposes:
- Sports diving can be done with air cylinders carried by the diver. This is called scuba diving. It can also be done for shorter dives by holding your breath. This is called freediving.
- Military diving
- Commercial diving is diving to do underwater work.
These can use various methods:
- Surface supply diving gets air for breathing through a hose from a pump above the water.
- Scuba diving is done with metal cylinders carried by the diver to hold the breathing air.
- Saturation diving is diving where the divers stay in pressurised rooms between dives and go to the underwater workplace and return in a sealed diving bell, so they stay at the same pressure for days or weeks at a time before the pressure is reduced to normal air pressure when they finish.
- Freediving is diving underwater without an air supply. The diver must hold their breath until they get back to the surface.