Which substance is most often used in recreational scuba diving?

The most commonly used substance in recreational scuba diving is air, which is a breathable mixture comprised predominantly of nitrogen and oxygen. When scuba divers descend underwater, they rely on compressed air contained in their tanks to provide the necessary oxygen to breathe while also allowing them to avoid the effects of high-pressure environments. The composition of air is ideal for recreational Scuba diving because it has a balanced ratio of oxygen that is sufficient for human respiration without posing significant risks associated with high partial pressures, as seen with pure oxygen or other gas mixtures.

In recreational diving, using air allows divers to maintain safe and manageable levels of nitrogen, which is important for avoiding decompression sickness. This aspect of air makes it preferable for standard diving practices. Although pure oxygen and helium have specific applications in advanced diving scenarios, such as deep dives or specialized technical dives, they are not typically suitable for recreational diving where the maximum depth and time limitations make standard air the safest and most practical choice for everyday diving adventures.