I'm a rebreather instructor in Grand Cayman. We see many rebreather divers come through here, and I see several common issues that are worrisome:
- Not understanding O2 sensors, their behavior, failure modes, and troubleshooting. This is the heart of the rebreather, you need to understand these backwards and forwards. I've had CCR divers tell me their brand new sensor is bad, because they installed it, and didn't understand they needed to calibrate it.
- Entering with gas turned off. Just in this thread, some have mentioned doing that. Sorry folks, that is inexcusable, and will lead to an issue one day when you don't pick up on it. Checking valves, and that all manual addition buttons work is part of the pre-jump check. Every student needs to tattoo this into their brains before I will sign off on them. Brian Buggee, and many others have died from hypoxic events from not turning their O2 on prior to jumping.
- Being overweighted. Many divers are using steel tanks when diving in warmer climates were the additional weight isn't required. The increased weight requires more air in the wing to offset and creates buoyancy issues.
- Bad configurations, sloppy rigging. I see many setups that are overly complex, and not much thought went into how the equipment is rigged. Many of these divers would be incapable of self-rescue should the need arise, because of their complex rigging. Your bottles and equipment should be streamlined, with no danglies, and you need to be able to don/doff the equipment unaided, both topside and underwater.