So, what is the deal with rebreathers? If you have seen any divers getting in the water with them, they look like something out of a science fiction movie. They also look far more complex and complicated than a set of mask and fins, an iPhone Underwater housing, or even some upmarket BCDs, but are they?
Is rebreather diving worth it? What do you get from it? Why would you want to go diving using a rebreather? Can you dive with rebreathers safely? There are lots of different questions and mysteries surrounding rebreathers and why you should and shouldn't use them. So check out what all the fuss is about rebreathers.
Rebreathers are Older Than Scuba!
Many divers think rebreathers are a modern invention, which is not true. Rebreathers are a much older invention than what we think of as open circuit scuba. Émile Gagnan and Jacques Cousteau invented modern-day scuba in 1942. However, rebreathers were theorized much earlier than that. In fact, attempts at producing a closed-circuit breathing system were made as early as 1876.
Rebreathers date to before WWI when the now famous rebreather company Draeger released its first rebreather in 1909. This unique unit combined a hard hat with a backpack featuring compressed O2. That being said, modern-day rebreathers are miles away from their ancestors, although the key principles of their operation are the same.
Why Use Rebreathers
Looking at rebreathers and wondering, "Gosh, these seem complicated; why would I bother ?" The answer is pretty simple and boils down to 3 different things, Bubbles, Gas and Money!
Marine Life Hates Bubbles
The bottom line is that lots of marine life species hate bubbles and are scared off by them. Many species associate bubbles with marine predators like dolphins, and the presence of a large black shape blowing bubbles makes them think they are on the menu. - Check out the video of humpback whales using a bubble net for hunting.
If you want to take some stunning images of creatures that are scared of bubbles and don’t want to come near them, your only option is to stop blowing bubbles. This is where rebreathers come in and why a lot of renowned underwater wildlife camera operators opt to dive with rebreathers since it gives them the freedom to get close to the action. You will notice this when you first dive a rebreather fish tend to react to you differently. They come closer than before and give you a new diving experience.
The Economics of Gas Management
Rebreathers are incredibly efficient when it comes to using gas. In fact, the main limiting factor with rebreathers is the duration of the scrubber material (the chemical used to scrub the CO2 out of your exhaled gas). This efficiency can be incredible when it comes to managing gas cylinders. To put the efficiency in perspective, imagine a single tank dive to 30m/100ft. On open circuit scuba, the dive would last about an hour and use one S80/12L cylinder. Using a typical rebreather, you could easily repeat 3 or 4 of those dives without the need to recharge your cylinders or scrubber.
This economy comes from the way rebreather work. Since, in essence, all a unit does is every now and then replace the small amount of oxygen your body has used by injecting some fresh Oxygen into your breathing loop.
The ability to be this economical is extremely handy if you're doing ultra-long dives. Imagine relatively shallow cave penetrations. The amount of open circuit gas needed is dramatically reduced. Since you only need to carry enough gas to get you back to the entrance from the farthest point of your dive!
Financial Savings
If you use a rebreather to trimix dive, the savings can rack up at an astronomical pace. Consider two divers doing the same 100-meter/ 330 feet dive in the Red Sea. After all, who doesn’t want to dive into warm tropical waters? Today the average cost of the gas in the open circuit divers set of doubles would be around $250. The diver would need a fresh fill virtually every day, so they would end up paying over $1,000 in gas just for the bottom mix.
If the diver has a friend diving with them on a rebreather, they would pay around $155 for their fills on day one. This would be around $30 for the small tank used in the rebreather and about $120 for an S80/12L cylinder to be ready as a bailout mix. Day 2 is where the savings start to add up. If there has been no emergency and the rebreather diver did not use the bailout, they can use it again the next day at no additional cost. The only cost they would incur is the $30 for a fresh mix for the rebreather. Over the course of the week, they would end up paying around $300 for the bottom mixes, which is a huge saving compared to the open circuit divers.
Looking at these savings trip after trip and year after year, it is clear why diving on rebreathers is much more economical, especially if you want to do mixed gas trimix dives.
Diving With Rebreathers
Although after a while, diving with a rebreather becomes second nature; however, when you first start, you will face a few challenges. These are due to rebreather diving requiring a slightly different skill set to open circuit diving. That being said it's always a fun experience to relearn and adapt your buoyancy skills and develop even better dive planning procedures.
Buoyancy Doesn't Work At First
One of the weirdest things you will notice when you first start diving a rebreather is that your buoyancy skill doesn’t seem to work anymore. You can’t breathe out a little to sink or inhale a little deeper than normal to rise. This is because when using a rebreather, you have a closed breathing loop, while with open circuit scuba, your loop is open.
When you exhale on open circuit, the breath is released into the water and ceases to act on your buoyancy. The Same happens when you inhale gas from the cylinder into your lungs, which now affects your buoyancy.
Using a rebreather, your lungs and unit counter lungs have a combined effect on your buoyancy. So whether the gas is in the Unit counter lungs or in your lungs, its effect on your buoyancy is the same! Therefore, inhaling or exhaling does not affect your buoyancy. The only way to alter your buoyancy is to add or remove gas volume from the system using an inflator or dump valve.
Taking your Planning and Bailout Skills to a New Level
Learning to dive with rebreathers will take your dive planning to a new level. You will learn to plan your dive with almost all contingencies taken into account. Learning what to do if you have malfunction, a catastrophic gas loss, or even an electronics failure is not only useful when diving with a rebreather but is incredibly useful when diving with open circuit scuba too.
In addition, you will learn useful skills like working out how much gas you need for a given dive. This makes planning regular scuba dives even easier since you can work out with confidence before the dive the logistics of gas management. You will also learn a host of dive planning skills in dealing with emergencies on the fly and getting yourself out of trouble. While some of these are rebreather diving specific, the majority cross over to open circuit scuba and are incredibly useful to learn!
Discipline is More Important With Rebreather
Diving with rebreathers requires much more discipline than scuba diving with open circuit. When using normal scuba diving, as long as your mask, fins, BCD, and Regulator are in good condition and well-serviced, you put your kit together and are ready to go. Before a dive, you perform a buddy check which takes a minute or so, and are done.
Rebreathers require far more discipline with maintenance and checks before a dive. Due to the system's complexity, the checks are more extensive and take longer. So, you need to be patient and disciplined if you want to dive rebreathers safely. If you are unwilling to do so and want to have a simpler pre and post-dive routine, then possibly rebreathers are not your best option.
Final Thoughts
Getting into using closed circuit units or rebreathers is a serious commitment to your diving future. Generally, the units are expensive, and few facilities offer rental options. Even then, rental costs are high, and if you are planning on rebreather diving regularly, you are better off biting the bullet and purchasing your own unit!
If you can arrange a trial dive on the unit or speak to friends who are rebreather divers, that would be great! But ultimately, you need to consider the pros and cons of rebreather diving and how it will change the way you dive. More importantly, you may want to consider whether you are willing to make the commitment.
Finally, if your answer is yes and you feel happy to make the financial and training commitment, then you are about to begin a new awesome underwater adventure! If not, you can still experience the ocean's majesty using open circuit scuba!
Investing in rebreathers or closed circuit units is a huge step toward a career in scuba diving. The condos tend to be pricey, and not many buildings have the option to rent them. geometry dash