Warning: This post contains many details from the movie.

As a tale of survival, "The Revenant" may have no recent peer. The new movie tries to kill off its Oscar-contending star, Leonardo DiCaprio, in just about every way you can imagine. DiCaprio, an 1820s fur trader on a mid-winter expedition, is mauled by a grizzly bear, stabbed and briefly suffocated. He is left for dead in a shallow grave, unable to walk, without food or water.

He drops hundreds of feet after flying head-long off a cliff -- on horseback, no less. The horse dies. Leo lives, his fall broken by tree branches. Even the threat of infection from the crudely sutured gashes opened by the grizzly is addressed in the film.

Yet  for a guy who froze to death in the open ocean in "Titanic," DiCaprio is impervious to the one thing that should have killed him: hypothermia. I lost count of how many times he plunged into an icy river or huddled and shivered on its banks, covered in layers of soaking wet skins and furs. DiCaprio and his fur-trapping compatriots also slog endlessly in the pouring rain and woodsy muck, evading Indians and, apparently, any reduction in their core body temperatures.

This irritated me during the movie, so I went back to a post I wrote a year ago, when former Miami Dolphin Rob Konrad fell off his boat near Miami and swam for 16 hours in the open ocean before washing up in Palm Beach. That water was about 70 degrees Fahrenheit. This was an icy river somewhere in the vast Missouri territory.

First, DiCaprio would have suffered the shock to the heart and uncontrolled breathing that results from plunging suddenly into cold water, Mike Tipton, a professor of human and applied physiology in extreme environments at Britain's University of Portsmouth told me then. "Sixty percent of those who die in [water] below 15 degrees [59 degrees Fahrenheit] die in the first minutes of immersion," he said.

But DiCaprio's as tough as they come, so let's say he survived that. Water conducts heat away from the body about 25 times faster than air, so it shouldn't be too long until his normal body temperature of 98.6 degrees Fahrenheit dropped below 95 degrees, the level at which hypothermia begins.

How long exactly? After pilot Sully Sullenberger famously landed a jet in the Hudson River in 2009, Scientific American asked emergency room physician Christopher McStay how long passengers could have survived in the 41-degree water.

"Generally, a person can survive in 41-degree F (5-degree C) water for 10, 15 or 20 minutes before the muscles get weak, you lose coordination and strength, which happens because the blood moves away from the extremities and toward the center, or core, of the body," McStay told the journal. People with a good deal of body fat may last longer, he said. But DiCaprio is clearly not among them.

Death itself takes longer, depending on the temperature of the water, according to a variety of online sources I consulted. For someone immersed in cold water that is below 32 degrees Fahrenheit, it could be as soon as 45 minutes, according to this web site.

This is worth knowing in mid-January of  2016, when fur trappers are no longer around, but hypothermia can hit the very old, the very young, people with mental illness or impaired judgement, people who have been drinking, and those with some medical conditions or on some medications, according to the Mayo Clinic.

Symptoms of mild to severe hypothermia include "clumsiness or lack of coordination, slurred speech or mumbling, confusion and poor decision-making, such as trying to remove warm clothes, drowsiness or very low energy, lack of concern about one's condition, progressive loss of consciousness, weak pulse and slow, shallow breathing." Left untreated, hypothermia will shut down your heart and respiratory system, causing death.

To be fair, "The Revenant" doesn't totally blow off the cold issue. There are a couple of times when DiCaprio and others carefully build life-sustaining fires. And it'll be a long time before I forget him doing the Luke Skywalker thing and crawling inside the carcass of his dead horse (after hefting and discarding some horse-sized internal organs).

I'm not sure that would have worked either, but that's a tauntaun of a different color.