This chart shows a dip in temperature and an increase in wind speed from 5-6 AM in Islip.
http://www.wunderground.com/history...Hauppauge&req_state=NY&req_statename=New+York
This shows average surface water temperatures at approx. 8 degrees Celsius (49 degrees Farenheit). I assume that the tidal marsh is somewhat close in temperature.
http://www.surf-forecast.com/breaks/Robert-Moses-State-Park/seatemp
This chart for Fire Island shows sunrise at 5:48 AM.
www.nps.gov/fiis/planyourvisit/upload/?2010_?TideTables.pdf
We know Shannan was known for discontinuing her medication. I think this may be the cause of her intense fear of death and flight that night:
https://en.wikipedia.org/wiki/Neuroleptics
"The psychological withdrawal symptoms can include psychosis, and can be mistaken for a relapse of the underlying disorder."
"Withdrawal-related psychosis from antipsychotics is called "supersensitivity psychosis", and is attributed to increased number and sensitivity of brain dopamine receptors, due to blockade of dopaminergic receptors by the antipsychotics, which often leads to exacerbated symptoms in the absence of neuroleptic medication."
"These adverse effects are more likely during rapid changes between antipsychotic agents, so making a gradual change between antipsychotics minimises these withdrawal effects."
https://en.wikipedia.org/wiki/Hypothermia
"Paradoxical undressing
Twenty to fifty percent of hypothermia deaths are associated with paradoxical undressing. This typically occurs during moderate to severe hypothermia, as the person becomes disoriented, confused, and combative. They may begin discarding their clothing, which, in turn, increases the rate of heat loss.[21][22]
Rescuers who are trained in mountain survival techniques are taught to expect this; however, some may assume incorrectly that urban victims of hypothermia have been subjected to a sexual assault.[23]
One explanation for the effect is a cold-induced malfunction of the hypothalamus, the part of the brain that regulates body temperature. Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a loss of vasomotor tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, fooling the person into feeling overheated.[23]
Terminal burrowing
An apparent self-protective behaviour known as terminal burrowing, or hide-and-die syndrome[24], occurs in the final stages of hypothermia. The afflicted will enter small, enclosed spaces, such as underneath beds or behind wardrobes. It is often associated with paradoxical undressing.[25]"
"Heat is lost more quickly in water[18] than on land. Water temperatures that would be quite reasonable as outdoor air temperatures can lead to hypothermia. A water temperature of 10 °C (50 °F) often leads to death in one hour, and water temperatures hovering at freezing can lead to death in as little as 15 minutes."
http://www.findshannangilbert.com/inside-the-investigation-part-1/
Last call to 911 ended 23 minutes after 4:51 (so 5:14 AM).
Based on my own personal experience, you can get lost in the woods in the dark even with a flashlight literally inside of 45 seconds after walking off the trail. You get disoriented very quickly and you need to repress your own panic. If Shannan ran into that tidal marsh, and she got wet, and she got lost, I guarantee she would be in a total panic. If she was wading through 49 degree water, she wouldn't have very long to live, especially if the wind picked up while the air temperature dropped.
She'd probably be close to death before sunrise. If she went into "terminal burrowing" inside that marsh, she probably covered herself entirely with reeds and muck. Finding her might be impossible even if a searcher were staring right at her. It will probably take 2 months of intense searching. I would comb over the area close to where they found the jeans multiple times.
