Scuba diving involves the use of some mandatorily required scuba diving equipment, mainly the underwater breathing apparatus.

Scuba sets comes in two kinds. The simpler one is the open circuit. Here, breathing in is done from the set while the outer breath just leaves the apparatus. This implies that the supply of gas lasts only as long as the re-breather set, and it would become very bulky if one was to carry more gas for loner diving. A demand regulator is present in the open circuit, and not a constant flow regulator. The latter maintains a constant flow of gas irrespective of the inhalation that takes place by the diver. This necessarily means that the dive will be of a shorter duration. But in case of demand regulator, the supply of gas is made only when demanded, that is, gas is supplied only when the diver inhales.

In comparison, a semi-closed or a closed circuit sets re-use the air exhaled, since just a fraction of oxygen is used by the lungs. Here, a carbon-dioxide scrubber [a soda lime cylinder] usually recycles the dead air, which renews the air for reuse. Though conservation of gas is done very efficiently by the re-breathers, they are not much efficient at deeper levels, which restrict their use to surface diving, which means a dive of anywhere between 6 to 10m.

To keep the diver at the depth that he wishes to remain at, the buoyancy compensator is generally used. These are packets bonded with the scuba set, and they inflate/deflate to let the diver float or sink, as he desires. Most of the buoyancy compensators have spots where divers can dump weights, to counterbalance the diving set's original buoyancy.

Electronic equipments are installed in most of the new scuba sets, which give the divers instructions about what action to take recourse to, or aid in regulation of proper gas flow. The divers can also carry with them a spare scuba set which can be helpful if the actual one doesn't function well, or they are required to stay under the water for a longer period than expected.

A harpoon is a must for underwater divers since you may find dangerous sharks and other animals underwater, who may try to harm you. Unless you are a superhuman, you can also take a waterproof camera with you to record the experience that you had underwater. Even otherwise, a camera will be a good thing to take as you will have the proof of having done adventurous things that you claim.