N.B - Do not attempt any diving that you are not qualified and certified to do. This article is simply informative and not intended to replace professional training courses.
You've passed your PADI Open Water or BSAC Sport Diver certification and now your off into the big expanse that is the ocean. One thing pretty much all of us divers have asked ourselves is 'what next?'
The chances are if you're a part of a scuba diving club or community, you will know a diver that is the epitome of 'All the gear, no idea'. If you don't, you're probably that guy (sorry!). They normally have countless cylinders and stages clipped to their wing and enough kit hanging from their D-Rings to stock a dive shop for a few months. Don't get me wrong, if the dive calls for it then take the kit but a 30 minute paddle around a 9 meter lake in Kent certainly doesn't call for 4 separate air sources and two different decompression gas blends.
When I started as a diver, I had no idea what the difference was between recreational and technical diving or why someone would want to carry so much equipment. So here is a bit about both, what it can open you up to, and which sort of diving might suit you better. Of course, don't run before you can walk!
This is it. If you've passed your Open Water / Sport Diver certification then you're officially a recreational diver! As the name suggests, recreational diving is all about diving to safe limits without pushing any boundaries set by your school and enjoying every second of the sub-nautical world. Some people start out in diving to see the plethora of marine life forms, from tiny nudibranchs through to Orca whales. Others are fascinated by shipwrecks and the history they hold, while some go diving simply for the thrill. No matter your reasoning, recreational diving accommodates it all.
OK so what's the difference? Technical diving is basically a step on from recreational diving. It takes what you already know and builds on it. Generally speaking, technical diving is any form of diving that goes beyond that of the restrictions in recreational courses. For example if you were to exceed the 'no decompression' limit you're now on a technical dive. Of course, you should never do that unless you've planned for it and are carrying the necessary gas blends and the right certification cards.
Technical diving was originally for extreme situations for commercial divers - deep sea exploration, military, salvage operations, that sort of thing. More and more in recent years though there's been an influx of recreational divers tiptoeing with the technical world. Rebreathers have been re-designed to accommodate recreational divers and several courses have been developed as 'crossovers' to aid a divers understanding of mixed gas diving. While commercial diving is still very different to recreational divers using technical training, the abyss between the two is narrowing. Of course there isn't just one way to go technical diving. The term is an umbrella for a range of skills and adaptations to suit various environments and dive profiles below the waves. The below are the most common but the possibilities and combinations are pretty much endless.
Decompression diving sounds a lot more radical than it really is. Simply put, decompression diving or 'going into deco' is simply exceeding the 'no decompression' limits set for a safe ascent. OK it's not as simple as it sounds as exceeding those limits poses several high-factor risks to consider. Decompression diving lends itself to more time beneath the waves and exploring that shipwreck. You'll find that you're no longer limited by time, but instead by the amount of air you're carrying on your back. This is why you'll often see decompression dives being conducted with twinsets or rebreathers, and a stage cylinder.
Extended Range Diving
Similarly to decompression diving, extended range diving simply is diving deeper and past the recreational threshold. If PADI's recreational limit is 40m then extended range tech diving is anything that goes below that. Anything as deep as 56.5m can be achieved on air with a PP02 of 1.4 (though nitrogen narcosis will be screwing with your mind) and anything deeper than that will require mixed gasses. As you go deeper, your 'no decompression' safe limits drop so you'll most likely find that if you're running an extended range dive, you'll probably also be running a decompression dive.
Mixed Gas Diving
This refers to any breathing gas (note the word 'gas' not 'air') that is more than just oxygen and nitrogen. It is quite common that helium will be added to the mixture for deeper dives in order to mitigate the effects of Nitrogen Narcosis, or that an accelerating decompression gas will be used at the end of a decompression dive in order to shorten the length of the deco stops on the way back up. Trimix (Oxygen/Nitrogen/Helium) and Heliox (Helium/Oxygen) are the two most common mixed gasses used, as well as an 'advanced nitrox' blend of a high o2 percentage (such as 80% oxygen) for various scenarios. As you'll be aware from your Open Water course, there are certain depths oxygen becomes dangerous known as hypoxic and hyperoxic mixes, so using these technical blends takes a deeper level of understanding and training in order to be sure not to breath the wrong gas at depth.
Twinset & Sidemount Diving
Carrying enough breathable resource is integral to survival below the water's surface, so 99% of the time a technical diver will use either twinsets, side mounts, or a rebreather to ensure their survival. That doesn't mean a huge dive has to be in the planning to get a new rig though! More and more recently, recreational divers have been opting for twinsets and sidemounts for the reassurance of a second cylinder available to them in case of emergency. The concept is used for carrying the additional volumes of air to be able to run a decompression or extended range dive and ensure that no-one runs out of breathable gas. Taking it a step further, some divers will also hang stage tanks on rope at various depths, or to the D-rings of their harness for additional blends. Twinsets and sidemounts are fundamentally the same in the sense that they both double the gas volumes you can carry. Twinsets are two cylinders (often banded together and manifolded) that are mounted on the divers back in the same way a single cylinder is, while a sidemount set up keeps the two cylinders separate, with one on each side of the diver and thus freeing up the weight on their back. Using these setups may look simple, but again takes additional skills and training in order to stay safe, so if you're interested ask your instructor for more information.
These are the divers you see and think they're part of the military. Normally with either big yellow or black boxes on their back, or large black canisters with cylinders either side, a rebreather diver is hard to miss. The principle of these is 'Closed Circuit' meaning that rather than breathing out a cloud of bubbles like 'open circuit' divers do, the exhaled breath is passed through a loop and into the canister on the divers back where excess nitrogen is cleaned out and additional oxygen is added if needed, then passed back to the diver once again. The machines - rebreathers - are complicated bits of kit but due to their very nature, can allow for much longer dives without carrying countless cylinders. They are normally used best when performing deep, long dives where the rebreather will automatically work out how much oxygen the diver can breathe safely and keep it at a pp02 point of 1.3. This means that rebreather divers will need to spend less time decompression than someone on the same dive using a twinset and mixed gasses. Often you'll find that only the most experienced divers venture as far as using one of these things. Plus, purchasing one new can set you back anywhere between £3,000 and £12,000. It all sounds pretty daunting, can anyone do it?
Yes. Gone are the days of hostility between recreational and technical divers. Nowadays there's often a hybrid of the two, and often all at different points in their diving lives. No one is exclusively ruled out from the option of technical diving, though many schools such as Tech Diving International (TDI) will have pre-requisites of what is required before a technical course can be booked in.
If you've only just started diving, enjoy where you are for now. Tech diving looks cool but it's not worth blowing hundreds or thousands of pounds on kit when you can still enjoy the recreational stuff. My advice would be to look to rack up around 80 to 100 hours underwater before moving into tech. You'll have perfected your skills and become calm and controlled in the watery environment. That will have the biggest benefit. But if you're ready to move on, get talking to your local scuba school or get in touch and we can advise further on what would be best for you.