Thanks for the added information. NO, I would NOT imagine that all would be ok. I can imagine all the things that can go wrong.
And yes we take risks, and yes we allow children to take risks, but when there is a risk of a fatality AND the parent CAN materially mitigate that risk by their presence, then they probably should do so. Perhaps that is something that can be learned from this horrible tragedy.
Also, simply increasing the instructor/professional to student ratio would in this case, probably NOT made any difference. The potential benefit of increasing the ratio is based on the underlying premise that the professionals involved would respond to an emergency in an appropriate manner. From what I have heard of this accident, they have clearly demonstrated that they would not respond in a reasonable manner.
In other words, if they (all) were too "stupid" to start looking for her when she was confirmed to be missing, how the hell can you assume they would diligently watch her - when the stakes were much lower?
One clown or 5, it still was obviously a circus.