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 level of professional disagreement as to what the term should encompass. Broadly, technical diving is any type of SCUBA that is considered higher risk that conventional recreational diving. However, some advocate that this should include penetration diving (as opposed to open-water diving, whereas others contend that pentrating overhead environments should be regarded as a separate type of diving. Others seek to define technical diving solely be reference to the use of decompression. Certain minority views contend that certain non-specific higher risk factors should cause diving to technical diving. Even those who agree on the broad definitions of technical diving may disagre on the precise boundaries between technical and recreational diving.

Depth

Technical dives may be defined as being either dives to depths deeper than 130 feet / 40 meters or dives in an overhead environment with no direct access to the surface or natural light. Such environments may include fresh and saltwater caves and the interior of shipwrecks. In many cases, technical dives also include planned decompression carried out over a number of stages during a controlled ascent to the surface at the end of the dive.

The depth-based definition is derived from the fact that breathing regular air while experiencing pressures causes a progressively increasing amount of impairment due to nitrogen narcosis that normally becomes serious at depths of 100 feet / 30 metres or greater. Increasing pressure at depth also increases the risk of oxygen toxicity based on the partial pressure of oxygen in the breathing mixture. For this reason technical diving often includes the use of breathing mixtures other than air.

These factors increase the level of risk and training required for technical diving far beyond that required for recreational diving. This is a fairly conservative definition of technical diving.