I definitely wouldn't jump straight to it being the gas mix that caused two children to drown together. That seems like one of the more unlikely scenarios.
I see as more likely, that one of the kids went down and put the reg in their mouth but inhaled a bit of water and choked on it setting up a cascade where one accidental drowning turned into two when the other child tried to save them and panicked, leading to the second drowning. Having experience on scuba would make this more possible because scuba helps us overcome the fear of breathing in while in a water environment but if you take a big inhale and it is wet, you can inhale water and start violently coughing. Heck, I can cough on the saliva produced by a cough drop or on a sip of water if I'm not paying attention.
Then there is the issue of horseplay and children failing to recognize the seriousness of what they are doing.
I suspect the autopsy will be helpful but we may never hear those results.
I see as more likely, that one of the kids went down and put the reg in their mouth but inhaled a bit of water and choked on it setting up a cascade where one accidental drowning turned into two when the other child tried to save them and panicked, leading to the second drowning. Having experience on scuba would make this more possible because scuba helps us overcome the fear of breathing in while in a water environment but if you take a big inhale and it is wet, you can inhale water and start violently coughing. Heck, I can cough on the saliva produced by a cough drop or on a sip of water if I'm not paying attention.
Then there is the issue of horseplay and children failing to recognize the seriousness of what they are doing.
I suspect the autopsy will be helpful but we may never hear those results.