Open-water diving

Open-water diving has at least two different meanings in scuba diving:

• In the later stages of initial diver training, divers progress from diving in swimming pools to "open water", which normally implies the sea or a lake, including quarries.
• Any diving where the surface of the water immediately above the diver is in contact with the Earth's atmosphere. "Open water diving" implies that if a problem arises, the diver can directly ascend vertically to the atmosphere to breathe air. Penetration diving—involving entering caves or wrecks, or diving under ice—is therefore not "open water"" diving.