Thanks all for the responses so far. I’m slightly intrigued by the science and mechanism of CO2 retention and panic now. Nitrogen narcosis is often talked about in cert classes but not CO2.
Yes, I have access to lots of those easy sites thankfully. I know I need to get “back on the horse” sooner rather than later, but ease back in.
For further reading the terms Hypercapnia and/or "dark narced" probably would be interesting.
Careful "full" breaths help me, both flushing out the bottom of my lungs (increasing tidal volume of my breaths) and to mentally calm (similar to helping with on land panic).
It's unfortunately easy to get co2 buildup and start feeling crazy/panicky. My brain goes irrational. Just takes a 2 minute breath hold at moderate depth to start wondering/feeling/frightened if a sea monster is behind me, my equipment is defective or I'm having a medical emergency. Horrible things mentally, all imaginary.
(Not a recommended test... I use it to see how co2 buildup effects me. Symptoms and severity varies against my own subjective baseline).
Never had a land based panic/anxiety and I'm a calm person (former first responder)... underwater "dark narced", my brain goes crazy with fears I didn't know anywhere else. It's remarkable.
Thanks for the post, it's something sometimes that isn't talked about much I think in training.
Also, glad you're planning to "get back on the horse" soon enough.