Tech Diving 101: Beginner’s Guide to Mastering the Depths

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Tech Diver with four tanks

Putting it simply tech diving is a more advanced type of diving that normally puts us beyond the no decompression limits of recreational diving.

For this type of diving, we of course need additional training and specialized equipment.

Tech divers exploring a shipwreck

This normally means that we no longer have direct access to the surface due to what we call a ceiling.

This can either be an actual ceiling preventing us from physically surfacing like diving in a cave or a wreck or it can be a virtual ceiling due to decompression obligations forcing us to gas off before we can ascend safely.

Tech diving can also be used by a diver to penetrate places normally unavailable with standard recreational scuba equipment due to its versatility and maneuverability.

For example, we may use a sidemount rig when attempting to pass through narrow cave systems or other tight spaces.

Tech diver exploring underwater debris

Don’t worry if you haven’t quite understood everything above. That’s what this article is about!

So if we’ve piqued your interest, read on and we will try to give you a full overview of the increasingly popular world of technical diving.

How does Tech diving differ from Recreation diving?

To put it quite simply, tech diving gives you the diver the opportunity once trained to spend longer at certain depths, penetrate overhead environments or venture way deeper underwater than recreation diving allows you.

If you have completed for PADI/SSI deep specialty course then you should be aware that your recreational depth limit is a maximum of 40m.

Using standard Decompression models anything below that would leave you with almost zero no decompression time and again that’s where tech diving comes in.

So, why Tech dive?

There are many reasons you may want to take up tech diving. Here are a few…


Some of the most stunning locations in the world are well out of reach of the average open-water diver and as a tech diver you have a big advantage here.

Wreck diving

Again some wrecks are either beyond the limits of recreational diving or at least partially unavailable. When tech diving you can go deeper and spend longer exploring these magnificent sunken treasure troves.

Scuba diver floating over a shipwreck

The challenge

Some recreational divers reach the point where scuba just isn’t challenging enough anymore and want to carry on learning and challenging themselves. Moving up through the tech system is not only challenging but presents an element of added danger that some people enjoy.

Marine life

There are many different marine species, especially pelagics and sharks that prefer the cold and dark of the deeper waters.

Tech diving again gives you access to see these beautiful creatures in their natural habitat.

Deep Sea Life on the ocean floor


Being a tech diver you have the opportunity to dive locations that have rarely or never even been seen by other divers.

You could even search for new dive sites and underwater coral beds for future divers to explore and enjoy one day.


Scientists and underwater researchers may opt for tech diving as they can go to greater depths and spend longer at depth to carry out scientific research, studies and surveys.

Equipment used for Tech Diving

There are 3 distinctive pieces of equipment used in tech diving.

Let’s have a look at what they are…

Tech diver with four tanks


Sidemount diving is very popular with cave/wreck divers and is when a diver uses a harness to attach 2 independent cylinders, 1 on each side of the body.

The cylinders are attached using a clip and D-ring system.

Using this system the side-mount diver can detach either or both tanks at any time and reposition them to change their profile.

This is extremely useful when moving through small spaces in a cave system or a wreck and gives the diver access to locations inaccessible to normal back mount divers.

On a deep penetration, a tank can also be completely removed and left behind and then recovered on the way back


Twinsets are 2 tanks that sit on the back. They are connected through something called a manifold. As this setup is essentially 2 tanks in 1, it can be pretty heavy when transporting.

One main advantage is that a diver can access both tanks with one single regulator as long as the manifold is open.


Rebreathers are definitely the preferred system for very deep diving. A rebreather is essentially a machine that regulates partial pressures within an exhaled gas and then loops it back around to the diver to be inhaled again.

JJ CR Rebreather product shot

When the diver exhales, the gas travels through a canister containing a special chemical known as Scrubber. The job of the scrubber is to remove excess carbon dioxide from the breathing loop. In addition, any metabolized oxygen will also be replaced into the breathing loop so that the diver will always be breathing the desired oxygen/nitrogen blend. The rebreather will adjust the gas levels automatically as the diver descends and ascends.

The main advantage of this system is that exhaled oxygen is looped back to the diver to inhale again which means that there is very little waste and the oxygen is used way more efficiently than with the regular scuba apparatus

Gas Blending

Enriched Air Nitrox (EANx)

Nitrox Chart comparing atmospheric air versus enriched air

This is really part of recreational diving but we are going to give it a mention as it is the first type of diving you will do that involves a gas mix that differs from standard air.

You will recognize the cylinders by the green and yellow labels that warn divers they are no longer breathing air and to take the necessary precautions.

Nitrox refers to any oxygen/nitrogen gas mix that has more than 21% oxygen. More oxygen reduces the amount of nitrogen in the gas mix. That means underwater you breathe less nitrogen and as a result, less nitrogen dissolves into the tissues allowing for a longer no decompression limit.

The more oxygen you add to a gas mix, the less deep you can go. So, Nitrox is purely a means of extending dives times and is not used for exceeding the standard recreational dive limits. That is where trimix comes in…


Photo by Trawangan. Dive

A major problem when breathing regular air underwater is that it contains 21% oxygen and when breathed below 60m becomes toxic due to the increased partial pressure within our bodies. This will result in oxygen toxicity causing convulsions and drowning.

To counter this problem tech divers use trimix. Within the mix both oxygen and nitrogen are decreased which will firstly reduce narcosis and secondly reduce the toxic effects of breathing oxygen and nitrogen at depth. Helium is then added to make up for the loss of other gases.

Helium is physiologically inert which means it has no toxic or anesthetic properties and does not act upon the heart or hemoglobin.

A tech diver uses low oxygen mixes on the descent and then high oxygen mixes during the final stages of the ascent to help gas off the additional accumulated nitrogen in the body

What are the risks involved with Tech Diving?

Nitrogen Narcosis

There are a few theories as to why nitrogen narcosis happens but realistically we as divers know relatively little about the causes. What we do know is that narcosis will induce a kind of anesthetic effect on us and as we go deeper the narcosis will keep on increasing.

Symptoms of narcosis include Euphoria, Tingling, Lightheadedness, anxiety, paranoia, memory loss, as well as numbness.

On top of that our situational awareness becomes compromised and we lose all track and perception of time and our ability to perform even simple tasks is impaired.

And to top it off we don’t even care that it’s happening to us!

Most divers will say they feel nothing and everything is going to plan!

The reason helium is used in trimix is to reduce the amount of nitrogen that we are breathing. That means that the effects of nitrogen narcosis will be less than if you were breathing standard air.

Oxygen Toxicity

There are 2 main types of oxygen toxicity.

The first is Central Nervous System Oxygen Toxicity (CNS) This happens when the partial pressure of oxygen within a gas mix exceeds 1.6 ATA at depth. To counter this tech divers breathe a gas mixture with a lower oxygen content called Trimix so that the partial pressure never exceeds the critical levels.

And the second is Pulmonary Oxygen Toxicity. This is caused when a tech diver goes to extreme depth or spends a large duration underwater as it will mean breathing an elevated PO2 level for many hours. This can cause irritation of the lungs

Tech diver exploring underwater debris

Decompression Sickness (DCS)

A big risk for tech divers is decompression sickness or DCS. It occurs when a driver ascends either too rapidly or with saturation levels of nitrogen too high in the tissues which can’t exit the body fast enough on the ascent. This will cause bubbles to form in the blood and tissues which can cause injury to tissues or cause small blood clots.

Long surface intervals are always planned on the ascent to allow the nitrogen to gas off.

For that reason, proper breathing and good buoyancy are 2 essential skills you need as a tech diver.

Female diver at a safety stop

How do I get started with Tech Diving?

The main 2 agencies you will come across when first looking into tech diving are TDI (Technical Diving International) and PADI TecRec.

With PADI you can even do a try tech dive which is similar to a regular discovery scuba dive but focused on tech. TDI also offers an intro to tech diving but it is way more in-depth as it is a 2-3 day course with 3 dives. For more information contact a licensed tech dive center.

So there you have it, a quick guide into the world of tech diving. Although there is an extra element of risk involved, proper training and disciplined planned diving will minimize all the potential dangers involved. Tech diving is enjoyed by people all over the world.

So if you already have diving experience and are interested in another challenge why not take a look into the world of tech diving?



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