An interesting story. I agree with the conclusion that the deceased contributed to their demise, although I'd personally put the value at higher than 85%...at least 95% IMO. My rationale is that the deceased clearly had absolutely no intention to freedive at all, because they were experienced and had explicitly chosen to leave their fins behind.Personally, what I suspect happened was that they wasn't feeling well (possibly because she was having a heart attack) and decided to enter the water for a float (hence, no fins). Submerging would have been more likely due ot a loss of buoyancy, such as by the lungs exhaling a little ... a likely evenf if one stops breathing while still on the surface. The air 'burp' was observed by the lifeguards was probably due to the body rolling over (mouth up), etc...about the only failure in diligence was that they allowed an individual who was supposed to be one of their peers venture into an out-of-bounds area. The consequences of this was that the deceased wasn't able to be rescued from 20-30fsw depths promptly by lifeguards, but this factor alone does not provide a high degree of assurance that the victim would have survived anyway. For example, there's ample examples of scuba divers who make it to the surface in distress (heart failure, etc) and even make it to the boat & pulled onboard ... but then die anyway.