Question Trying to decide on a rebreather unit

[Dann-Oh]

Hey all,

I'm trying to decide on a unit. I'm between the Kiss Sidewinder, Hollis Prisim P2, and DiveRite Choptima.

I know they are all different types or rebreather units.

Pros:
Sidewinder: I really love diving sidemount on OC.
Choptima: I can just add it to my OC Sidemount kit, I can also add it to my Backmount single tank for recreational diving.
Prisim P2: a local instructor who I trust a lot teaches 100m on the P2. He has nothing but good things to say about it.

Cons:
Sidewinder: Can be tough to get used to diving CC sidemount on local boats, they aren't the biggest fans of OC sidemount
Choptima: I don't have a local instructor (5hr drive) BUT I know several locals who dive the unit.
Prisim P2: A back mounted unit and its the unit I know the least about. But I have seen it in action several times.


I want to get into advanced shipwreck diving, penetration diving on the wrecks in San Diego, Ca. I would love to visit the wrecks up in the great lakes (Lake Huron) at the 180-200ft (60-67m) depth. There is a lot to see here in Southern California as well. I know I wont be able to afford tec diving on OC for very long so I'm thinking I just make the transition to CC sooner than later. I can do a lot of diving on AIR DIL here locally.

What are your thoughts on the 3 different rebreathers I have shortlisted?

 

[grantctobin]

Hey all,

I'm trying to decide on a unit. I'm between the Kiss Sidewinder, Hollis Prisim P2, and DiveRite Choptima.

I know they are all different types or rebreather units.

Pros:
Sidewinder: I really love diving sidemount on OC.
Choptima: I can just add it to my OC Sidemount kit, I can also add it to my Backmount single tank for recreational diving.
Prisim P2: a local instructor who I trust a lot teaches 100m on the P2. He has nothing but good things to say about it.

Cons:
Sidewinder: Can be tough to get used to diving CC sidemount on local boats, they aren't the biggest fans of OC sidemount
Choptima: I don't have a local instructor (5hr drive) BUT I know several locals who dive the unit.
Prisim P2: A back mounted unit and its the unit I know the least about. But I have seen it in action several times.


I want to get into advanced shipwreck diving, penetration diving on the wrecks in San Diego, Ca. I would love to visit the wrecks up in the great lakes (Lake Huron) at the 180-200ft (60-67m) depth. There is a lot to see here in Southern California as well. I know I wont be able to afford tec diving on OC for very long so I'm thinking I just make the transition to CC sooner than later. I can do a lot of diving on AIR DIL here locally.

What are your thoughts on the 3 different rebreathers I have shortlisted?

They’re all totally different and there are a slough of threads talking about each of them. If your goal is to do bit dives off of a boat, a sidemount unit is not the solution. Source: have done some 100m dives with a sidewinder off of a boat. It is a shitshow.

I don’t know anyone that dives a P2 that wasn’t given one or teaches on one. That said, it’s the traditional unit on your list.

If the above are truly the only units you’re considering, why not grab a BM Optima and then later down the line get a chest conversion kit?

In the end, I’d figure out what the people around you are diving as well as trying to figure out competence of instructing. There’s decent Choptima and P2 instruction within a few hour drive from you all the way through advanced mix. I do not personally know of any competent SW divers in the area.



But hey, at least you didn’t say you wanted a KISS Go

 

[rjack321]

Hey all,

I'm trying to decide on a unit. I'm between the Kiss Sidewinder, Hollis Prisim P2, and DiveRite Choptima.

I know they are all different types or rebreather units.

Why these units? I particular there are a ton of others with a mismash of features overlapping these 3

 

[Dann-Oh]

They’re all totally different and there are a slough of threads talking about each of them. If your goal is to do bit dives off of a boat, a sidemount unit is not the solution. Source: have done some 100m dives with a sidewinder off of a boat. It is a shitshow.

I don’t know anyone that dives a P2 that wasn’t given one or teaches on one. That said, it’s the traditional unit on your list.

If the above are truly the only units you’re considering, why not grab a BM Optima and then later down the line get a chest conversion kit?

In the end, I’d figure out what the people around you are diving as well as trying to figure out competence of instructing. There’s decent Choptima and P2 instruction within a few hour drive from you all the way through advanced mix. I do not personally know of any competent SW divers in the area.



But hey, at least you didn’t say you wanted a KISS Go

I'll have to look into the optima backmount unit. I didn't realize there was a chest mount conversion for it.

I know of a small group that dives Revo units.

I only know 3-4 people personally that dive rebreathers and they all dive different units. 3 of them are 60+ meter divers and 2 are 100m divers.

I do most of my diving in Southern California, I don't travel for diving.

 

[Dann-Oh]

Why these units? I particular there are a ton of others with a mismash of features overlapping these 3

I'm open to other units, I think. I'm going to add the Optima backmount unit to my list as well.

 

[RedSeaDiver2]

I want to get into advanced shipwreck diving, penetration diving on the wrecks in San Diego, Ca. I would love to visit the wrecks up in the great lakes (Lake Huron) at the 180-200ft (60-67m) depth. There is a lot to see here in Southern California as well. I know I wont be able to afford tec diving on OC for very long so I'm thinking I just make the transition to CC sooner than later. I can do a lot of diving on AIR DIL here locally.

This sort of diving is what divers in the UK do every weekend, and in the UK they mostly dive with back-mounted units, and off the top of my head I can't think of any chest or side mount rebreathers that were developed in the UK - but they have developed the JJ, the Inspo and probably some others so I think that there is a message in there somewhere for you about what sort of unit you probably should be considering for your sort of diving.

Looking at back-mounted units, the most well-developed, advanced ones include the Tiburon, the XCCR, and the Divesoft Liberty. I've just been through the same decision-making process as you are going through, and the process I went through was to look at all of the well-established options on the market to see what was available, what features on each I liked, what I didn't like etc.

The net step was to list all the things I didn't like, and the badly designed things - and then place them on a list and decide which ones I could live with, and which ones I couldn't live with. Carry that across to the list of rebreathers and then cross off the rebreathers that had things I couldn't live with.

Then do much the same with a list of the good things - create a list of them all, decide what I couldn't live without, carry that across to the list of rebreathers and cross off the ones that didn't have those essentials.

Then compare the remaining rebreathers on the list with your likes but not essentials and your don't like but can live with - eventually you will work your way down to just 2 or 3 rebreathers left to choose from. That is the point where you need to then start learning a lot more about each one and reading the forums about each one - partly to find out what improvements are in development for each one - this is important as there could be something in development for one of them that completely changes the picture for that rebreather and makes it a clear winner even though it had something that I didn't like but decided that I could live with.

 

[Tassi Devil Diver]

For the type of diving you are doing I would not discount the rEvo, of the back mounted rebreathers it has probably the lowest profile and small form factor making a good wreck diving and general boat diving unit (takes up less space). It is small and compact and just capable as any other unit.

 

[Wibble]

@Dann-Oh - the best rebreather is the one you are using and have experience of diving.

Assuming from your post that you've not dived rebreathers before and you've no experience with them. That's good; we all started from there

Rebreathers need a LOT of practice and constant diving. They're not like changing from single-tank to twinset to sidemount; rebreathers are very different than open circuit. This implies that you'll need to select one rebreather and dive it regularly for a couple of years or more, especially as you're talking about deep diving (100m/330ft).

You've mentioned three different styles of rebreather: backmount (good for boat/wreck diving and deep), sidemount (specialist, awkward) and chestmount (not good for deep).

My personal advice to you is to choose a common and well-regarded backmount unit. Only when you're experienced with diving a rebreather -- meaning at least a couple of hundred hours/dives -- should you then consider something different.

Common units that are well regarded are probably the ones you've seen on your dive boats already. For example the JJ and Revo. Many others are available.

My diving is on a Revo; I dive in the UK (cold water) predominantly off of dive boats for the past 5 years down to 75m/250ft. This works very well and the Revo has been a very reliable unit which I've no intention of changing. It also works well in overhead environments provided they're not too wriggly.

As long as you choose a common and well regarded unit, it should suit you well for boat diving.

You must budget for the training and practice diving you will need. I've no idea what your current diving is but the Divemaster qualification is of no real benefit. When diving a rebreather, you'll naturally want to dive deep (meaning trimix) and long (meaning substantial decompression). If you've those skills already, then you'll be well prepared for some aspects of rebreather diving. If you've been predominantly diving to NDLs and nitrox; there's a lot more to learn before you can head down to deep and long.

The first course will be your "MOD1" which is how to dive the unit and do some light decompression, possibly with trimix but normally you'd probably get qualified on nitrox to either 30m/100ft or 40m/130ft. A few experienced divers with exceptional skills or prior trimix & deco experience may pass the 45m/150ft MOD1 but they’re the exception.

Once you have MOD1, you must do 100 hours of diving on it in different locations including shallower locations where you constantly run through your skills and get the buoyancy sorted out. Buoyancy on a rebreather takes a lot of time and effort to master and be comfortable, especially shallow 6m/20ft (which you'll be spending a lot of time at whilst decompressing from deep dives).

Only after getting very comfortable in your unit and mastering the various skills learned on your MOD1 will you move on to MOD2. Doing this early is not recommended as it will be a miserable experience (just like doing twinset skills if the basics aren't good).

MOD2 is about decompression diving and staying alive on the unit when you've a considerable decompression obligation. You'll be bailing out to open circuit trimix and practising endless skills for keeping your unit running if, for example, you've run out of gas, there's been electronic failures, etc. MOD2 dives are generally around the 2h to 3h duration with 1h to 2h30 decompression times.

Again, after MOD2 you'll need to do a lot of practice and actual dives to master those skills. At least you'll now be "qualified" to do 70m/230ft dives, so well set to develop your wreck diving experience.


Rebreathers are massively useful tools for diving; incredibly flexible and quite cheap to run in comparison with open circuit. They come at a cost of complexity and greater levels of planning and preparation.

It would help if you've a friend/buddy you could do the journey with. Someone to "play" and practice with is an excellent help, especially when doing the endless skills practice.

Selecting the rebreather is the easy bit!

 

[rjack321]

It would help if you've a friend/buddy you could do the journey with. Someone to "play" and practice with is an excellent help, especially when doing the endless skills practice.

Selecting the rebreather is the easy bit!

There is definite merit in selecting a unit that is common in your area and general circle of divers. And something that has a good instructor corps - this is one area where the sidewinder and Prism in particular are dubious. The Choptima is better in this regard.

I would add the x-ccr, JJ, backmount optima, meg, and even revo to the list of reasonable units for So Cal boat diving. I'd remove anything sidemount or chest mount.

 

[inquis]

You also need to decide electronic (solenoid injection) vs manual (leaky or needle valve) control of PO2. Some with an eCCR unit will perform frequent manual O2 injections (push a button) and leave the solenoid as a backup (so called "parachute mode").

The eCCR category is pretty well represented by earlier posts. The Fathom is an example of a backmount unit with needle valve. Some can be setup as hybrid (leaky valve and a solenoid).

There are pros and cons to each type. Keep this in mind when going through the numerous earlier threads in the RB section.