These are a few different diving modes:
Diving as a leisure activity is called sport or leisure diving and has been divided into different sub-areas. The differences can be determined on the one hand by the type and scope of the equipment used and on the other hand by the goal pursued during diving.
Apnea (free) diving
Apnea diving is the oldest and most original form of diving. Free diving takes place with your breath held without artificial respiratory air supply, whereby the diver is often only equipped with ABC diving equipment and a diving suit. Apnea diving is practiced both as a general and competitive extreme sport. There are different disciplines such as static time diving, distance diving or deep diving. However, apnea diving is the most widespread in the world in the form of underwater hunting.
A special form of apnea diving is snorkeling. The diver or snorkeler swims on the water surface using a snorkel and briefly dives to shallow depths without a breathing apparatus. Often people snorkel to observe the underwater world or to save water.
The underwater sports of underwater rugby and underwater hockey use surface snorkeling to follow the game. However, the players dive down to intervene in the game and are then freedivers.
When scuba diving, the diver uses a compressed air diving device (SCUBA) or a circuit diving device (rebreather) to survive under water. Thanks to the artificial breathing gas supply, dives of several hours are possible. Most of the time, physical activity, fun, relaxation, adventure and nature observations are the main motivations for diving. Scuba diving is the most widespread type in the world today. Around 1.7 million people are trained as scuba divers every year. When diving, compressed air or nitrox is usually used as the breathing gas and not, as is sometimes assumed, pure oxygen. Depending on the exposure time, this has a toxic effect on the central nervous system from a partial pressure of 1.4 to 1.6 bar (from approx. 6–7 meters depth when using pure oxygen or about 67 meters when using compressed air with 21% oxygen) and creates oxygen poisoning. Therefore, recreational divers usually do not exceed a depth of 50 meters (a few diving organizations even allow 60 meters) and only stay under water for around an hour. Diving is usually done in a buddy team or a small group to increase safety. For scuba divers there is a large selection of equipment and a wide range of diving training.
Technical diving (Tec-Diving) is an increasingly popular special form of scuba diving, which enables recreational divers to undertake deeper and longer dives using techniques and processes that were originally reserved for professional diving. The boundary to normal scuba diving is fluid. Originally one spoke of technical diving if the breathing gas mixture was changed several times in a single dive. Today there are also definitions independent of the breathing gas.
As a rule, the breathing gas mixture is changed several times in a single deep dive, since each mixture has different advantages and dangers at different depths. As a result, some divers get into the water with numerous bottles. Technical divers use equipment such as wing jackets, full face masks, stage bottles, backplate with harness and others that go beyond the usual level of recreational diving. Technical diving requires specific, advanced training because of the different equipment and the special breathing gases.