Technical diving (sometimes referred to as Tec diving) is a form of scuba diving that exceeds the scope of recreational diving (although some technical divers dive for recreation and nothing else). Technical divers require advanced training, extensive experience, specialized equipment and often breathe breathing gases other than air or standard nitrox.
Technical divers may use unusual diving equipment. Typically, technical dives last longer than average recreational scuba dives. Because required decompression stops act as an obstacle preventing a diver in difficulty from surfacing immediately, there is a need for redundant equipment. Technical divers usually carry at least two tanks, each with its own regulator. In the event of a failure, the second tank and regulator act as a back-up system. Technical divers therefore increase their supply of available breathing gas by either connecting multiple high capacity diving cylinders and/or by using a rebreather. The technical diver may also carry additional cylinders, known as stage bottles, to ensure adequate breathing gas supply for decompression, with a reserve for bail-out in case of failure of their primary breathing gas. The stage cylinders are normally carried using an adaptation of a sidemount configuration.
These types of overhead diving can prevent the diver surfacing directly:
* Cave diving - diving into a cave system.
* Ice diving - diving under ice.
* Wreck diving - diving inside a shipwreck.
Extremely Limited Visibility
Technical dives in waters where the diver's vision is severely impeded by low-light conditions, caused by silt or depth, require greater knowledge and skill to operate in such an environment, and because vision is often reduced by water currents. The combination of low visibility and swift current make these technical dives extremely risky to all but the most skilled and well-equipped divers.
Inability to ascend directly
Technical dives may alternatively be defined as dives where the diver cannot safely ascend directly to the surface either due to a mandatory decompression stop or a physical ceiling. This form of diving implies a much larger reliance on redundant equipment and training since the diver must stay underwater until it is safe to ascend or the diver has left the overhead environment.