Technical Diving allows experienced divers to dive deeper, enter overhead environments such as a wreck or caves or dive for longer bottom times with specialised equipment after gaining expert training.
Technical or deep dives are defined as dives deeper than the standard recreational limits of between 30-40m. This is due to the fact that breathing regular air while experiencing depths below 30m causes an increasing amount of impairment due to nitrogen narcosis.
Technical diving is also described as dives that are long enough to require mandatory decompression stops which can be performed using nitrox or pure oxygen. Decompression diving carries higher risks as it is no longer safe to make a direct ascent to the surface when underwater problems occur. That's why obtaining the necessary technical training is essential before you consider this type of diving.