Technical diver

Technical diving (also referred to as tec diving or tech diving) is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to greater risk of serious injury or death. The risk may be reduced by appropriate skills, knowledge and experience, and by using suitable equipment and procedures. The skills may be developed through appropriate specialised training and experience. The equipment often involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.

The term technical diving has been credited to Michael Menduno, who was editor of the (now defunct) diving magazine aquaCorps Journal. The concept and term, technical diving, are both relatively recent advents, although divers have been engaging in what is now commonly referred to as technical diving for decades.

There is some professional disagreement as to what exactly technical diving encompasses. Nitrox diving and rebreather diving were originally considered technical, but this is no longer universally the case as several certification agencies now offer Recreational Nitrox and recreational rebreather training and certification. Some training agencies classify penetration diving in wrecks and caves as technical diving. Even those who agree on the broad definitions of technical diving may disagree on the precise boundaries between technical and recreational diving.

The European diving agencies tend to draw the line between recreational and technical diving at 50 metres (160 ft) and many teach staged decompression diving as an integral part of recreational training, rather than as a "bolt-on" extra.

The following table gives an overview of the activities that various agencies suggest to differentiate between technical and recreational diving:

One of the perceived differences between technical and other forms of recreational diving is the associated hazards, of which there are more associated with technical diving, and risk, which is often, but not always greater in technical diving. Hazards are the circumstances that may cause harm, and risk is the likelihood of the harm actually occurring. The hazards are partly due to the extended scope of technical diving, and partly associated with the equipment used. In some cases the equipment used presents a secondary risk while mitigating a primary risk, such as the complexity of gas management needed to reduce the risk of a fatal gas supply failure, or the use of gases potentially unbreathable for some parts of a dive profile to reduce the risk of harm caused by oxygen toxicity, nitrogen narcosis or decompression sickness for the whole operation. Reduction of secondary risks may also affect equipment choice, but is largely skill-based. Training of technical divers includes procedures which are known from experience to be effective in handling the most common contingencies. Divers proficient in these emergency drills are less likely to be overwhelmed by the circumstances when things do not go according to plan, and are less likely to panic.

...
Wikipedia