Dan, there is quite a broad range of rebreathers available these days, new and used, but I'll try and answer some of the questions you raised and comment on some of the points made.
fookisan:
When I ask at the scuba shop or at the dive resorts I come up with nothing.
No doubt more scuba shops carry OC gear than rebreathers. In areas where there are enough divers to support rebreathers you'll find stores having them on display or in stock. Some have a Dräger SCR or two, the most popular (and oldest consumer) semi-closed rebreather available. There are a few 'rebreather shops' in areas that have multiple instuctors or instructors with multiple ratings that support multiple models and types.
There are resorts catering to RB divers, as well as dive boats and liveaboards. You just have to look for them. Take Belize for example, dozends and dozends of dive shops, but at Protech Belize you'll find SCRs and CCR (including rentals), training, supplies and day trips.
Why are rebreathers not more mainstream if they are so good?
A couple of factors:
- price, for initial unit purchase, additional training and maintainance
- additional maintainance
- additional training, you need type rating for RBs, training on one doesn't mean you can dive another
- you pretty much start from scratch
- different failure possibilities and different actions to take
- less support by shops (absorbant, gasses, supplies and spares)
- people don't know much about them and don't bother to change that
Are they a pain in the *** to maintain?
Depends a lot on the unit, a MK series or Cis-Lunar can be quite difficult and very expensive to maintain, a Sport Kiss or Dolphin quite easy. But there are more components to clean, assemble and vigilantly check for correct operation. A simple hose down after a dive weekend isn't gonna do it.
The only benefit I know of with rebreathers is silent diving - which I sometimes would enjoy after prolonged shallow diving and getting sick of the bubble noise in my ears. Any other benefits?
They all extend the dive duration you'll get from your gas. Even cmf-SCR like the Dolphin will keep you in the water longer, depending on the nitrox based flow rate. RMV keyed SCRs extend that again, about 1:8 regardless of depth (used with nitrox or trimix). With a CCR, where the loop is closed (until ascent, then they vent like a BC) gas savings are multiple times that. Only metabolized O2 gets replenished, around 1 lpm at light workload. A small 2 liter cylinder (13 cuft) at 200 bar will last for hours.
That can translate into enormous gas savings when diving trimix (He costs around 80¢/ cu ft, so filling twin 98 with 10/50 will cost $80 or more ... and last less time!).
SCRs run of nitrox (or trimix), so you get the same advantages as OC nitrox.
CCRs, instead of using a fixed gas mix, use a fixed pO2 setpoint. For example 1.2 ata, and mix the O2 and the diluent (air, trimix or heliox) on your back so that the partial pressure of the oxygen stays the same at different depth and the mix changes. That will give you the 'best mix' for the depth you're at, increase your NDL and decrease deco when you incurr it.
Is it expensive to get into?
As mentioned above, there is a broad range of rebreathers.
From the $1,800 Dräger Ray to the $15,000 Ouroboros.
Semi-closed units range from the Ray to the Halcyon RB80 at around $8,500.
Manually controlled CCRs are between $4,000 and $5,500.
Most electronically controlled CCRs are between $7,500 and $10,000.
A few eCCRs are in the $15,000 range, even used.
Where would one start to discover diving with rebreathers?
Reading, really. There are some good sites on the web, such as Rebreathers Worlwide and Rebreather World. Jeff Bozanic's book "Mastering Rebreathers". Rebreather forums. Major dive shows usually are attended by at least some of the manufacturers.
Then find an instructor for a unit you're intrested in and try it. Do a rebreather intro. Get trained, go dive and get experienced. Don't get complacent.
