Found a web site that teaches investigators about drowning:
"Experts consider some individuals who drown as victims of dry drowning. In these cases, the fatal cerebral cerebral hypoxia or oxygen deprivation, does not result from water occluding the airway but, rather, from a spasm of the larynx. Water never enters the lungs. These instances constitute 10 to 15 percent of all drownings.
When people sink beneath the surface of the water, they initially react by holding their breath. This continues until they have to breathe, thereby involuntarily inhaling a large volume of water, which either enters the lungs (in most instances)
or reaches the larynx -- producing a larygeal spasm that results in dry drowning. In both cases, this gasping for air may continue for several minutes until respiration ceases. Cerebral hypoxia will progress until it becomes irreversible and death occurs..
Investigators can look for some distinctive signs to determine cases of drowning. Officers must recognize these indicators and then articulate them to the medical examiner. Presently, no known and proven pathological test exists to determine drowning as the cause of death, so, by itself, an autopsy usually proves insufficient. Authorities can make this diagnosis only with a knowledge of the circumstances and exclusion of other causes..
Over the years, experts have developed and tried a number of tests to determine conclusively whether a person drowned. All have proven unreliable on their own. No morphologic findings diagnostic of drowning exist. Although an autopsy usually is not sufficient by itself, it can exclude other possible causes of death.."
Source:
Drowning investigations. - Free Online Library
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The Coroner's Report stated that Tina suffered a laryngeal spasm, which as it states above causes a "dry drowning." So if Tina still had the reg in her mouth as was reported by multiple people, including Watson, at the moment he left her - she may have attempted to tightly breathe through the reg until she suffocated rather than breathing in water. Still, at least a small amount of water may have entered her lungs. My personal opinion - if she drowned because she had panicked, the reg probably would have been out of her mouth because she would have taken in a large volume of water as described above in the 85-90% percentile of drowning cases. Seeing how only 10 to 15% of drownings are "dry drownings" such as Tina's - I would say that the reg held tightly in her mouth as she "drowned" increases the likelihood as the reason for the finding of laryngeal spasm, otherwise known as "dry drowning."
So to answer Bruce's question of even if Gabe Watson hadn't left her, would she still have died from whatever it was that she died from? I think she would have survived if she had gone diving with anyone else but him because I think there would have been air provided to the reg she so desparately hung onto in her mouth and she would have kicked to the surface, as was her initial panic reaction during her cert dives.