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My rebreather class report (and first rebreather dive).

Discussion in 'Rebreather Diving' started by Preach, May 2, 2021 at 1:42 PM.

  1. Preach

    Preach Rebreather Pilot

    # of Dives: 200 - 499
    Location: Nederland
    About a year ago i posted a thread on this forum asking for advice on rebreathers. I came to the conclusion i wanted a well maintained/not to old inspiration. It is what my buddy is using and it's an affordable machine. I live close to the uk and we have a AP dealer in my country as well.
    It toke a little longer than expected but i found and bought a 2013 inspiration with a monochrome handset, in a travel frame. 3l bottles and a 2.5kg scrubber. Almost no scratches (bought it from an OW diver) and not
    discolored. I was able to buy it for a really nice price as well.

    This weekend was finally the time for my first 4 dives of the mod1 course. The instructor traveled to me, cause i have some nice lake's around where i live. Friday we did some theory till 11 pm and we got up early, around 6 am. Time for my first rebreather experience! I knew up front that it was going to be a different kind of class then my cave/tech classes, a lot of people told me it's like starting all over again. And that was also how mentally prepared myself for the course.

    Dive 1:
    At the dive site we did all checks and entered the water. It was an easy dive site, the bottom gets deeper really slow. So what could possibly go wrong? :p.
    We tried to descent but i didn't have enough lead. The instructor pulled some extra lead from her pocket so we didn't have to walk back to the car. We tried to descend again, and this time it worked. I fell in a flat trim, and could hover above the bottom..... not bad, right?.....
    Then she pointed into a direction, and we started swimming and descend more, slowly. Suddenly i felt like i needed to put in more effort to breath, but i was still ok. I started to have more trouble with my buoyancy, i really had a high taskload to keep everything in order. I could hardly see my handset nor my computer, the loop was in the way, turning my head didn't go easy. It all felt really strange! After 10 min of botttomtime i burped up some breakfast into the loop (just a really small amount tho).
    I noticed that my breathing became faster, and i had troubles to maintain everything. I knew the gas from the loop was good (prebreath, tempstick etc), but it got worse and worse. At first i just told myself to relax, breath slowly and it would be ok. But i started to feel really terrible, till the point i couldn't handle it anymore. I switched my bov to oc and tumbed the dive. The instructor checked my gear fast (she didnt see anything strange) and grabbed me by my arm, she knew i would forget to dump my counterlungs. She helped me with the ascend, which went pretty well, she had to pull me down a little tho.
    At the surface i told her what happend. I was in a slightly negative trim, which made breathing slightly harder. That combined with the taskload (yes, just swimming on the unit was enough) was to much. I told her i needed a few minutes to calm down before trying again. After a small break we descended again. Descending was pretty easy. I let myself fall out of trim a little (feet slightly down) which worked a lot better on the breathing part. At this point she just helped me to dive around a little, so i would become more confident on the unit then at the first part. And that worked out nice.
    At 9 meters of depth i was having a hard time keeping my buoyancy, not noticing the unit switching from low to high setpoint of po2 but i managed. After this we swam back and left the water.

    My feeling was somewhat mixed, i had the feeling this was going to be a hard one to master. I didn't know how to feel about the second dive.
    I did know (from oc experience), i had to move some lead up, from my waist to higher on the unit. The slightly positive trim is caused by heavy feet and overcompensating for that.
    We also talked about the po2 low and high limit. Tips like, breath out of the nose when the unit does that or (even better) manual add some o2 before the units does that. Don't rely on the unit for everything, take control and check everything.

    Dive 2:
    The next dive my trim was a lot better, 1kg of lead higher up the unit worked well. The unit breathed loads better, at least in my experience at that time.
    We ascended slowly, following the bottom. Then she wanted me to show her i could operate all the parts of the unit, valves/dumps/mavs. While i could operate everything, i still had a hard time. The lack of muscle memory sucked, i felt like a true beginner in diving :p.
    Then i had to show a bailout to my bailout stage, it went ok but i didn't do it in the right order which made it sloppy. The loop never flooded tho.
    After that we made a ascent from 8 meter to the surface, not following the bottom. I could maintain my stops, but it must have looked pretty weird. I had to get out of trim, forgot my counter lungs/breathing out through the nose (gas just escaped from my mouth), had to swim down at parts..... She was happy that i controlled my ascent, but it was sloppy.
    The next exercise was descending and swim to 15 meters (high po2 setpoint was put to 15m) and keep my buoyancy while the solenoid added the o2. I also noticed the solenoid clicking a lot of times in a row, cause i exhaled 0.7 po2 compared to the setpoint of 1.3 po2.
    After that we swam back and slowly ascended following the bottom.
    At this point i could remain my buoyancy while swimming, but crashed into the bottom at the moment we stopped.

    My feeling about diving on the rebreather was a lot betyer then the first dive, but still far from the security i have on my oc set!
    I never did something uncontrolled, just really sloppy. And it still felt like an enormous taskload.
    At moments i was just frog/backkicking just to keep my platform.

    In the evening we went through some theory and checked all our stuff for the next day. We also needed some fillings, apparently i used shitloads of diluent being sloppy :eyebrow:.

    Dive 3:
    We went to a deeper lake. We would slowly descend into the depth and see how it goes, then slowly move up. O2 was being done manual for this dive. We prepared everything and jumped in.
    The first minute i needed to get my buoyancy straight (so touched the bottom a few times), then we went off. From this point on i didn't hit the bottom for 20 minutes while swimming above it while descending slowly along the bottom. It actually felt good! We hit 27 meters and turned the dive, this is where the taskloading started.
    I was really busy keeping my buoyancy, and for some reason i had a hard time dumping my suit gas. Never uncontrolled, but it was hard work. At this moment i was getting more feeling with the loop volume and how to use it better. Probably still while wasting too much diluent gas compared to more experienced rebreather divers.
    When we hit the 20m point we came to a steep part in the profile of the bottom. She waited and stayed close, just to see what would happen. I swam around a little, taking a part that was a little less steep. Hitting the bottom in progress, dammit.
    When we came in shallower water she demonstrated how to pump up my po2 to 1.6 and how to flush it down, opening the counterlung and checking the cells. The excercise itself was going well, while having a hard time to maintain buoyancy.
    After that i had to pop a SMB. She looked like she said, figure it out how you going to do it.... I switched to oc, inhaled, popped the smb and went back on the loop right away. It went pretty good, still messing around with the buoyancy of course.
    After the dive she explained some other methods to pop a smb.

    At this moment i noticed some things improved fast but at some points the taskload was still high. I did get the feeling i would probably going to like this kind of diving, for the first time.

    Dive 4:
    For this dive i was manual going to inflate the diluent and we would swim through some very easy objects to put my buoyancy and trim to the test. We are both cave divers and the objects are simple, no hazard at all.
    First we went trough a small object were i had to unclip my bailout and keep it in front of me. This went well, there was a part where i forgot my diluent tho. I had no problem inhaling a bit less till i added some.
    After this we went to an object that is around 3 meters high from the bottom up (10 meters deep). She signed that i had to swim over it, instead of around it. At this part the small ascend went really controlled/slow and in trim. well and she cheered..... a little.... so it seemed to me..... (ok maybe). The descents never seemed like a problem. We swam through the object a few times. there isn't a lot of space and i had to use my finger a few times to keep my platform.
    After this she told me to switch to my offboard bailout gas and we swam around a little. After a few minutes she tumbed the dive. I thought, this is going to be simple. An ascend on oc. But at 6m i had to switch back on the loop and maintain my platform. After that we ascended very very slow, i was able to keep it up till 1.5m. I felt way better then the first dive, but there is still so much to improve. I'm not even close to my oc buoyance.

    I probably forgot some stuff and exercises. I'm not the best in writing things down, Especially not in English.
    But since i don't see a lot of reabreather course write ups, i think it has some added value.
    I did the first 4 dives of the course, the rest comes later on.

    Some poeple have a bad first rebreather experience, in try-outs and such. So had i in the first part of this course (first 15 min), but it gets better really fast. My advice would be not to quit to fast :p. They really work great after some practice.
    TTPaws, stuartv, 1c3d1v3r and 7 others like this.
  2. irycio

    irycio DIR Practitioner

    # of Dives: 100 - 199
    Location: Switzerland
    Nice report, thanks for sharing! I recently started diving in a mixed team as a buddy of mine did MOD1 (I'm still far from that) and watching him struggle I can only imagine what the course looks like ;-).
    Preach likes this.

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