Technical diving can be described as dives that are long enough or deep enough to require mandatory decompression stops using high O2 percentage nitrox or pure oxygen. Decompression diving carries higher risks as the diver cannot 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. Taking technical diving even further is introducing the use of hypoxic breathing gas mixtures such as trimix. Breathing air at depths greater than 55m increases the risks of symptoms of oxygen toxicity resulting in seizures and often drowning. Adding helium to the breathing mix can reduce both the percentage of oxygen and nitrogen allowing deeper dive depths.

Technical diving can involve a significantly longer time in the water than recreational diving, therefore it is necessary to increase the supply of breathing gases by connecting multiple diving cylinders or by using a rebreather. Technical divers also carry reserve equipment and gases should they experience failure from their primary source, which is why you will see technical divers with much more equipment than recreational divers.

This style of diving is not for everyone. Because of the increased risks you must be willing to accept these before starting down the tec route. The rewards though can be amazing. You get see dive sites that are too deep for recreational divers.

You have to accept the extra investment in equipment and training you'll have to make. But if you like equipment and gadgets and a challenge, then tec diving could be for you.

Most diver these days have at least heard of Nitrox, or Enriched Air Nitrox, but may not be too sure what it actually is, so nitrox is air with extra oxygen added into the mix. By adding oxygen, the nitrogen is reduced, which in turn reduces the narcotic effects of the breathing gas. As every diver will know, nitrogen is the controlling factor for no decompression diving, by reducing the nitrogen, the no decompression times are increased, as well as adding conservatism to the dive planning.

Nitrox can be considered the first step down the tec route.

Trimix is made up of helium, oxygen and nitrogen, and can be considered at the pinnacle of technical diving. By adding helium, the nitrogen is reduced, thus reducing the narcotic effects of the breathing gas at depth. With less nitrogen, trimix divers are able to go deeper, and then also "select" the amount of narcosis they want to have. Now if the diver reduces the oxygen content too, well then the diver can go even deeper. In theory, by choosing the right combination of helium and oxygen percentages, the trimix diver can go as deep as he wants to.

Trimix diving requires a significant level of experience, training and equipment.