Last year one of my longtime scuba dreams came true: I became a technical diver. Over the past few months, I posted a lot on Instagram about the training I did, and the number 1 question I get asked is always ‘what is technical diving?’. It’s usually followed by an apology for not knowing, but it’s not a stupid question at all. For the longest time all I knew about technical diving was that it looked cool and involved a lot of tanks. So for all of you that were (secretly) wondering, here’s a beginner’s guide to technical diving!

The definition of technical diving

There can be some disagreement about what exactly is the definition of technical diving. But it is generally accepted to say that technical diving includes all diving activities in which you intentionally exceed recreational depth (40 meters/130 feet) and time limits, and plan for it accordingly. A technical diver deals with a ceiling that (temporarily) prevents him to ascend to the surface. Think about a cave or a wreck, or a virtual ceiling in the form of a decompression stop. What is meant by this is that in case of an emergency, the diver can’t go straight up to the surface. Technical diving comes with a higher risk than recreational diving, and technical dive training teaches a diver how to handle those risks. It requires a certain level of dive skills, knowledge of dive theory, and comfort level.

Teamwork is incredibly important in technical diving. Being a good team member starts with being a good dive buddy in recreational diving. Take the quiz to find out what type of dive buddy you are!

Types of technical diving

There are different types of technical diving. All of them have unique characteristics and potential hazards, but what they have in common is the inability to ascend directly, the so-called ceiling. It’s important to note that each type of technical diving requires specialized training.

Overhead environments (physical ceiling)

  • Cave diving
  • Wreck diving
  • Ice diving

In these types of diving, a lifeline is attached from the exit to the diver, to reduce the risk of not being able to find the way out. I will not go into much detail of diving in overhead environments – not only because I personally have zero experience in it – but also because it goes beyond a general introduction of technical diving.

Open water decompression diving (virtual ceiling)

Technical dives are typically deeper and/or longer dives than recreational dives, and therefore require staged decompression stops before going back up to the surface (a virtual ceiling). Some people say that every dive is a decompression dive, because every dive involves the compression and absorption of nitrogen upon descent, and decompression and elimination of nitrogen upon ascent – no matter how shallow or short the dive. The difference is that in recreational diving, you stay within the ‘no decompression limit’ (NDL) – which is indeed a deceiving term – that allows you to go straight to the surface at any time, without a reasonable risk of decompression sickness (DCS).

In technical diving, you typically and intentionally exceed the NDL, and plan staged decompression stops on your ascent. This gives your body time to release the excessive nitrogen in your body, eliminating a reasonable risk of DCS. You can see these staged decompression stops as multiple mandatory safety stops in varying length, at different depths during the ascent. Failure to conduct a decompression stop will likely result in DCS. However, the chances of a diver getting DCS cannot be simplified by (not) staying within the NDL or (not) completing staged decompression stops. There are many factors that contribute to someone’s susceptibility to DCS, and may even vary from day to day for the same person. It is therefore recommended to always dive conservatively, even when diving recreationally, and not get too close to your NDL.

Technical diving equipment

Technical diving requires a lot more equipment than recreational diving. The magic word here is redundancy. Because a technical diver’s inability to directly ascend to the surface, he needs to have a backup of every equipment item in case of failure.

This may include, but is not limited to:

  • Mask + back up mask
  • Tech friendly dive computer + additional timing device
  • Slate
  • 2 SMB’s
  • Spool or reel long enough for the deepest depth
  • Two high performance regulators
  • ‘Oxygen clean’ regulator when diving with 40% oxygen or higher
  • Torch + back up torch depending on light penetration
  • Tech shorts to stow all accessories safely
  • Back up mouthpiece
  • Bolt snaps

But the most noticeable difference with recreational diving is the amount of tanks. Because technical dives are typically deeper and longer, a single tank doesn’t hold enough gas to complete them in a safe manner. On top of that, the various tanks of a technical diver may contain different gas mixes. For example, a diver may choose to bring a tank with Enriched Air Nitrox of up to 100% oxygen to speed up the decompression process. Another gas that’s commonly used is Trimix, a mix of oxygen, nitrogen and helium, to decrease the effects of gas narcosis.

Technical diving configurations

Just as there are different types of technical diving, there are different configurations, each with their own advantages and disadvantages.

Twinset (or doubles)

In a twinset configuration the diver carries two tanks on his back. Both tanks are connected to each other by a manifold, which is a kind of bridge between the two tank valves. The manifold allows the diver to access the gas supply from both tanks through one single regulator, although he will still use two first stage regulators (redundancy!).

Twinset configuration: two tanks on the back, and possibly one or more decompression tanks on the side.

Because both tanks are attached by a manifold, only one LPI and SPG are used. If the diver also carries one or more decompression tanks (with Enriched Air Nitrox) these are attached to the diver’s harness on the left side.


When diving twinset, the diver wears a backplate and wing with a harness. The backplate and harness may be the same as for recreational diving, but the bladder is bigger than a single-tank bladder. This is of course needed to make room for the two tanks, but also because a technical setup is much heavier than a recreational setup, and therefore requires a higher lift capacity.


In the sidemount configuration a diver carries his tanks on the side, alongside his torso, instead of on his back. Sidemount finds its origins in the world of cave diving, as it allows a diver to maneuver in tight spaces like caves or wrecks.

Each tank has its own regulator and spg, and because the tanks are not connected to each other by a manifold, the diver has to switch between tanks throughout the dive. This way he continuously has a (more or less) similar gas volume in both tanks to keep the weight distribution balanced.

A sidemount diver carries his tanks on his side, alongside his torso.
Photo by Pete Nawrocky


Because the diver doesn’t carry any tanks on his back, a specialized harness and bcd are required. The bladder is much smaller than that for a back mount configuration, and kind of looks a tiny backpack!

Although sidemount was originally only used by cave divers, this is no longer the case. It’s becoming increasingly popular for open water decompression diving and even recreational diving. Many divers love the freedom of movement it gives them in the water, and it can also help to improve trim.

Long hose configuration

In technical diving the primary second stage is attached by a long hose, which the diver donates to another diver when sharing air. He then switches to his secondary second stage on a short hose that he carries around his neck with a  bungee-cord necklace. This is an important difference with recreational diving, where the alternate air source has the longer hose, and the diver keeps his own primary regulator when sharing air.


A rebreather circulates the gas that is exhaled by a diver.
Photo by Dr Lyn Turner

A rebreather circulates the gas that is exhaled by the diver, removing carbon dioxide and adding additional oxygen. The main advantage of rebreather diving is more efficient use of gas. Because exhaled gas is recycled over and over again, a diver can last much longer on the same air supply. This advantage becomes even more significant the deeper you go. It is for this reason that rebreathers are commonly used for (very) deep dives in technical diving.

Another advantage of rebreathers is the absence of bubbles when diving (except on ascent). This makes it a suitable option for military divers who want to sneak up on an enemy, or marine biologists and photographers who want to get up close to their subjects without scaring them away.

Rebreathers are much more complex and therefore more costly and more prone to failure than open circuit scuba (the more common type of scuba diving where a diver’s exhaled gas is released in the form of bubbles). 

Dive planning

Beside the inability to ascend to the surface at any moment, there is one more thing that all variations of technical diving have in common: they require extensive planning. Every new diver learns in the Open Water Course that he should always plan a dive – but let’s be honest – not many people actually do that. We jump in and follow our dive computer, and this generally works out well. In an emergency – your equipment fails or you run out of air – you simply go up to the surface and swim back to the boat or shore. When a technical diver faces an emergency he has two options: solve the problem at depth, or go up to the surface anyway (if he can make it) and accept the fact that he will most likely get DCS. That really isn’t a very good option, hence why dive planning is so important.

Dive planning starts with information gathering: establish the dive objectives, dive site information, equipment needs and information about the dive team. The dive should always be planned based on the abilities of the least experienced diver. Then the team decides on the actual dive plan and gas requirements for each member. To determine gas requirements it is essential that you are familiar with your average air consumption – and that of your team member. If he has a gas failure at depth, you should carry enough gas to get both of you back to the surface safely while still following the decompression schedule.

A technical diver often writes the decompression schedule on an arm slate.

During the dive, the dive plan is continuously monitored and adjusted if necessary. No matter how well you plan the dive, things can always change. This is why it’s common to make contingency schedules; for example one for staying for a longer or shorter time than planned at the deepest depth, and one for the loss of a decompression tank. Throughout the dive, team members continuously keep each other updated on their gas consumption and other vital information. Directly after the dive there’s an evaluation to determine what went well and what should be done differently in the future.

The risks of technical diving

By now it’s probably clear that technical diving is more risky than recreational diving. Some of the most important risks are:

Decompression sickness

Failure to complete staged decompression stops will very likely result in DCS.

Gas narcosis

Both oxygen and nitrogen are narcotic at depth, and can cause an anesthetic effect that leads to impaired judgement and paranoia (among other things).

Oxygen toxicity

Oxygen becomes toxic when inhaled in high concentrations, which happens at depth. When using Enriched Air Nitrox, a diver has to be conscious of its maximum operating depth (MOD).

Task loading

All that extra equipment and safety measures also mean more tasks to complete – before and during the dive. Tasks that may be easy at the surface or even on a shallow dive, can suddenly become daunting at depth.

Equipment failure

No matter how well you prepare or maintain your equipment, a failure can still occur. Although it’s common to carry backup items in technical diving, a simple equipment failure can easily become a serious problem when not dealt with accordingly.

The inability to go directly to the surface

Problems that arise have to be solved at depth. There is no room for panic in technical diving. 

These risks don’t necessarily mean that technical diving is more dangerous than recreational diving, although my mom probably wouldn’t agree with that. A dive is only dangerous if someone is not properly trained for the type of diving he’s doing. A shallow dive by a diver who forgot everything he learned in his Open Water Course is far more dangerous than a dive at 100 meter by a well trained and well prepared diver, who is familiar with the risks and knows how to handle them accordingly. Technical dive training is very extensive and prepares you to handle these risks. Self-awareness, situational awareness and teamwork are extremely important. 

technical diving Requirements

If you’re anything like me, you want to become a technical diver after reading this! There are various training agencies that offer technical training, and their requirements and course setup may vary:


TDI is the leader in technical diving and it’s who I did my training with. To enroll in the TDI Advanced Nitrox and Decompression Procedures (ANDP) course, you need to meet the following requirements:

  • Minimum age 18
  • Minimum certification of Advanced diver or equivalent
  • Proof of 25 logged open water dives

Visit their website more for information.


To enroll in the PADI Tec 40 course, which is their entry level technical training, you need to be:

  • A PADI Advanced Open Water Diver
  • A PADI Enriched Air Diver with at least 10 dives using Enriched Air deeper than 18 meters/60 feet
  • A PADI Deep Diver or proof of at least 10 dives to 30 meters/100 feet
  • At least 18 years old and have a minimum of 30 logged dives

Visit their website for more information.

There are other training organizations that offer technical dive training, such as (but not limited to) GUE, RAID, and NAUI. You may choose one over the other based on personal preference and availability in your area.

Final word of advice

I hope you now have all the information to decide if technical diving is something you want to try. If it all seems a bit daunting at the moment, that’s nothing to be ashamed of. In fact, I believe you should only start your technical diving path when you feel like you have nothing left to learn in recreational diving, and you feel 100% comfortable at all times. If this is not the case, then it might be a good idea to hold out for a bit longer. It took me many years to finally proceed to technical training, and I’m really glad I did because the skills and experience I built during that time allowed me to get the most out of my training.

If you’re looking for an easy way to document your dive experience as proof to enroll in a technical dive course, click here to download my free dive log template!

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