I am often asked why I prefer to dive a rebreather over open-circuit scuba.  My reasons are mixed and sometimes maybe a little hard to quantify.  But the simple answer is, for me, it has a number of advantages over traditional scuba.

Key Advantages of Rebreather Scuba Diving

While a rebreather isn’t the best choice for every diver or every diver, it is the best choice for many dives and many divers. Poseidon, a rebreather manufacturer says the key advantages are, a rebreather system is less noisy than an open-circuit system, making the interaction with marine life more intense and up close, as wildlife will approach you rather than swim away from you. The duration of a dive on a rebreather system is generally much longer which means that you can either stay down longer in one dive or do several repetitive dives without the need to re-fill your cylinders. The reason for this is that you will not use up your gas as fast as on a normal scuba system, because you are re-using gas the whole time, making the rebreather 96% efficient in comparison to 4% efficiency during an open-circuit dive. Your gas costs will be reduced, especially when you venture into technical diving. No decompression time is far greater on the rebreather system as it makes sure you have the optimal gas mix at every depth, therefore minimizing the intake of nitrogen. If you are a certified Nitrox diver, you can compare it to having a nitrox blender on your back that makes sure that you have the best mix at every depth.
An open-circuit system gives you cold and dry gas, but on a rebreather you will get moist and warm gas, which is much more comfortable to breathe while diving. There is no need for deep breaths because the loop is an extension of your lungs. You only need to make sure that you continually breath normal breaths. Your buoyancy will not be altered by the way you breathe; it will only be changed when you add gas to your buoyancy device. 

Noise – a Rebreather Dive is Quiet

When I first started diving, I loved the silence that the underwater world brought.  The sounds of traffic, phones, engines and other people faded away and the only thing you heard was the sound of your own breathing in the bubbles as they raced past your ears.  Switching to a rebrerather brought new sensations.  The surface sounds faded away just like on open-circuit scuba but so did the noise created by the bubbles.  Suddenly it was really quiet — at least until I swam near a reef.  Then I heard it — the sound of millions of small shrimp clicking away on the reef.  Yes, as the sound of my bubbles faded, I was suddenly able to hear the sounds of nature and the reef and it was so cool!
When you get used to the relative quiet of the rebreather, you can really tell when open-circuit divers are approaching.  The bubbles are so noisy and the fish begin to hide!
I know this is a politically incorrect statement but it is true.  This is one of the reasons some rebreather divers do not want to dive with the “bubblers.”  Of course there is another side to this; many open-circuit divers do not want to dive with rebreather divers because they take longer to get ready to go diving.

Time – a Factor In and Out Of the Water

This is true, especially when compared to single cylinder, recreational diving.  A rebreather diver has a checklist for the assembly and preparation of the unit for use underwater.  Working through this checklist is a thirty minute to an hour process depending on the unit and the experience of the diver.  Most times the divers get up a little earlier to complete the diving but there are times that gas is delayed or other logistical factors do not align and the open-circuit divers are stuck waiting for the rebreather divers.
But, once the divers are in the water, the rebreather shines.  Having a “custom gas blender” on your back means that you get the optimal breathing mix throughout the dive.  As we noted above, this translated into longer no-decompression times or shorter decompression profiles when compared to most open-circuit profiles.  My first rebreather dives were amazing.  I was in Grand Cayman swimming along the wall at 80 fsw to 100 fsw for an hour and then up along the top of the wall for the second hour and by the time I reached the mooring line there was no decompression time and I could go straight up.  Of course, like all good divers, I did a safety stop but you can imagine my delight at doing a two-hour dive with no decompression required.  Of course that changed later that year when I discovered the sponge belt in Grand Cayman at about 180 fsw.  Now a limited amount of decompression was required.
On another occasion, when I was diving with mixed teams (open-circuit and closed circuit rebreather divers) in Florida a few years ago, we found that the rebreather divers could stay on the bottom, exploring the wrecks ten to fifteen minutes longer than the open-circuit divers and still exit the water at about the same time.  In other words, we spent more time exploring wrecks like the Hydro Atlantic,  and less time hanging in the water column decompressing.

Weight – Lighter is Better

My diving has changed a lot over the years.  I started in single cylinders, and then moved up to twin cylinders or double cylinders when I started cave diving and wreck diving.  As my cave diving progressed, I found that I wanted more air so heavier cylinders were needed.  At some point, Cliff Simeneau talked to Ann about the newest trend sweeping diving in the US and the importance of offering training on this new technology.  We had already been diving and teaching the Drager Dolphin Semi-Closed rebreather systems but this was the time when the Inspiration was beginning to be seen in the US.
One of the advantages of a rebreather is that it gives you the same or more duration as the twin cylinders without the weight of the cylinders.  So, I was overjoyed at trying the unit and diving it more.  It is funny, one of my instructors, Tom Mount, liked to comment that the difference between new rebreather divers and more experienced rebreather divers was that at some point, experienced divers started making comments about how heavy their rebreathers are.  This means they have now forgotten the shift from the much heavier cylinders to the lighter rebreather and now the CCR unit is the focus of the weight in their mind.
So, yes, a CCR unit is lighter than a set of twin cylinders – even the Sentinel weighs less than a twin-set of  cylinders.  Over the years, CCR units have become lighter and more compact.  Several of the newer models, like the Pathfinder from Inner Space Systems, weigh closer to a single cylinder set-up which makes them ideal for travel.  This reduced weight is also easier on your back as a diver which is important as the diving population ages.

Interaction – The Marine Animals Play More with Scuba Divers in a Rebreather

While weight and time are important factors for a rebreather diver, one of the most exciting things is the interaction with marine animals.  Let’s face it, bubbles are noisy and the fish react differently when there are bubbles.  The small fish move into the coral with each release (i.e. with each exhalation) and other animals just move away.
One of the first things i noticed a rebreather were those small fish moving in and out of a coral head.  I had spent countless hours photographing coral heads, trying to get the timing right so I could photograph of the fish suspended above the coral.  On my first Inspiration CCR reef dive, I noticed the fish remained suspended above the coral head; they did not disappear into the coral with my breathing!  I also found the lobsters remained out on the reef rather than backed up into a hole.  Perhaps the most amazing thing was coming face to face with a spotted eagle ray over a wall.  It was so cool!
The life under the sea is so different without the noise of open-circuit scuba.  As a rebreather diver you get to experience the world like a free diver but you get to stay and keep enjoying it while the free divers head back to the surface.  Imagine coming face to face with a large turtle or a ray or watching squid mate or even being surrounded by large tarpon or schools of fish.  This is rebreather diving on a reef!

Cool – You just look really cool Scuba Diving in a Rebreather

What can I say, you just look like James Bond!  Because they are still rare at a lot of dive sites, when you dive a rebreather you will attract attention and people will stop and ask you questions.  This may not be the ideal situation if you are a c overt operative but it does lead to some interesting conversations.  It is also fun to surprise other divers underwater when you swim by — remember they did not hear you coming.  But let’s face it, diving is pretty cool and rebreather diving is definitely cool!
So, why isn’t everyone diving a rebreather?  I ask myself that all of the time.  People will tell you it is the cost, or the time or the commitment which are all good reasons but when you try one, you will see why rebreather divers are hooked.  They have found the money, time and made the commitment to experiencing the underwater world to its fullest.
Isn’t it time you joined the new rebreather diving generation?