Found this on another site and thought some might be interested - even if our water is generally a bit warmer than the region referred to.

Sourced from http://gcaptain.com/maritime/blog/drowning/

The Truth About Cold Water

I’m going to come right out and tell you something that almost no one in the maritime industry understands. That includes mariners, executives, managers, insurers, dock workers, for certain – fisherman, and even many (most) rescue professionals:

 

It is impossible to die from hypothermia in cold water unless you are wearing flotation, because without flotation – you won’t live long enough to become hypothermic.

 

Despite the research, the experience, and all the data, I still hear “experts” – touting as wisdom – completely false information about cold water and what happens to people who get in it. With another season of really cold water approaching, I feel compelled to get these points across in a way that will change the way mariners behave out there on (or near) the water.

 

What follows is the truth about cold water and cold water immersion. I know that you think you know all there is to know about hypothermia already (and maybe you do), but read ahead and see if you aren’t surprised by something.

 

When the water is cold (say under 10 degrees C) there are significant physiological reactions that occur, in order, almost always.

 

You Can’t Breath:

The first is phase of cold water immersion is called the cold shock response: It is a stage of increased heart rate and blood pressure, uncontrolled gasping, and sometimes uncontrolled movement. Lasting anywhere from 30 seconds to a couple of minutes depending on a number of factors, the cold shock response can be deadly all by itself. In fact, of all the people who die in cold water, it is estimated that 20% die in the first two minutes. They drown, they panic, they take on water in that first uncontrolled gasp, if they have heart problems – the cold shock may trigger a heart attack. Surviving this stage is about getting your breathing under control, realizing that the stage will pass, and staying calm.

You Can’t Swim:

One of the primary reasons given by recreational boaters when asked why they don’t wear a life jacket, is that they can swim. Listen up, Tarzan; I swam for a living for the better part of my adult life, and when the water is cold – none of us can swim for very long. The second stage of cold water immersion is called cold incapacitation. lacking adequate insulation your body will make its own. Long before your core temperature drops a degree, the veins in your extremities (those things you swim with) will constrict,  you will lose your ability control your hands, and the muscles in your arms and legs will just flat out quit working well enough to keep you above water. Without some form of flotation, and in not more than 30 minutes, the best swimmer among us will drown – definitely – no way around it. Without ever experiencing a drop in core temperature (at all) over 50% of the people who die in cold water, die from drowning perpetuated by cold incapacitation.

 

You Last Longer than You Think:

If you have ever heard the phrase, “That water is so cold, you will die from hypothermia within ten minutes.” then you have been lied to about hypothermia. For that matter you can replace ten minutes with twenty, or thirty, or even an hour, and you’ve still been lied to. In most cases, in water of say 5 degrees (all variables to one side), it typically takes a full hour to approach unconsciousness from hypothermia, the third stage of cold water immersion.  But remember, you must be wearing flotation to get this far.

We are all different in this regard, but I once spent an hour in 7 degree water wearing street clothes and my core temperature was only down by less than two degrees (I was not clinically hypothermic). It was uncomfortable to be sure, and I wouldn’t recommend finding your own limit, but it probably would have taken another hour to lose consciousness, and an hour after that to cool my core to the point of no return. The bodies efforts to keep the core warm – vasoconstriction and shivering – are surprisingly effective. The shivering and blood shunting to the core are so effective, that twenty minutes after jumping in (twice the “you’ll be dead in ten minutes” time), I had a fever of 37.9.

 

Rescue Professionals Think You Live Longer:

There is a good side to the misconceptions about hypothermia. Should you ever be in the water in need of rescue, you can be certain that the Coast Guard is going to give you the benefit of every possible doubt. When developing search criteria – search and rescue coordinators use something called the Cold Exposure Survival Model (CESM): It is a program wherein they enter all the available data about the victim (age, weight, estimated body fat, clothing, etc.) and about the environment (water temp, sea state, air temp, wind) and the software spits them out a number that represents the longest possible time you can survive under those conditions. I plugged my own information into it once and it said I could survive for over 4 hours in 3.5 degree water wearing nothing but a t-shirt and jeans and no flotation. I can tell you from experience that the CESM is full of it – I’d give me 35 minutes tops – but the error is comforting. If the program that determines how long I might live is going to be wrong – I want it to be wrong in that direction.

 

Out of the Water is Not Out of Trouble:

I lost count of the number of survivors I annoyed in the back of the helicopter because I wouldn’t let them move.  I had a rule – if they came from a cold water environment – they laid down and stayed down until the doctors in the E.R. said they could stand.  It didn’t matter to me how good they felt or how warm they thought they were.  Because the final killer of cold water immersion is post-rescue collapse.  Hypothermia does things besides making everything colder.  Victims are physiologically different for awhile.  One of the things that changes is called heart-rate variability.  The hearts ability to speed up and slow down has been effected.  Getting up and moving around requires your heart to pump more blood, being upright and out of the water is also taxing, then any number of other factors collide and the heart starts to flutter instead of pump – and down you go.  Victims of immersion hypothermia are two things; lucky to be alive, and fragile.  Until everything is warmed back up – out of the water and dry is good enough – mobility comes later.

 

Did You Learn Anything?:

If you did, then hopefully you’ll use it to make good decisions when it comes to being safe on and around cold water; good decisions like these:

1. When working on deck, wear flotation.  This includes, especially, all fisherman in Alaska.  I couldn’t find more recent research, but the 31 Alaskan “fell overboard” casualties in 2005 died from drowning, not cold water.  Not one of them was wearing flotation.  Many couldn’t stay above water long enough for their own boats to make a turn and pick them up…..over a life jacket.
2. If you witness a man overboard – getting the life ring directly to them is critical (vital – step one – must do it).  Make certain that all-important piece of safety gear is not just on your vessel, but readily available and not tied to the cradle.
3. When working on deck – wear flotation.  I said that already? Well, when I quit reading search reports that end with “experienced” mariners dying because they thought they understood cold water – I’ll come up with better advice.

For more advice about how to handle an accidental immersion into cold water
– please watch http://www.youtube.com/watch?v=J1xohI3B4Uc
– it is one of the best 10 minutes on immersion hypothermia ever produced.

 

Drowning Doesn’t Look Like Drowning

 

The new captain jumped from the cockpit, fully dressed, and sprinted through the water. A former lifeguard, he kept his eyes on his victim as he headed straight for the owners who were swimming between their anchored sportfisher and the beach. “I think he thinks you’re drowning,” the husband said to his wife. They had been splashing each other and she had screamed but now they were just standing, neck-deep on the sand bar. “We’re fine, what is he doing?” she asked, a little annoyed. “We’re fine!” the husband yelled, waving him off, but his captain kept swimming hard. ”Move!” he barked as he sprinted between the stunned owners. Directly behind them, not ten feet away, their nine-year-old daughter was drowning. Safely above the surface in the arms of the captain, she burst into tears, “Daddy!”

 

How did this captain know, from fifty feet away, what the father couldn’t recognize from just ten? Drowning is not the violent, splashing, call for help that most people expect. The captain was trained to recognize drowning by experts and years of experience. The father, on the other hand, had learned what drowning looks like by watching television. If you spend time on or near the water (hint: that’s all of us) then you should make sure that you and your crew knows what to look for whenever people enter the water. Until she cried a tearful, “Daddy,” she hadn’t made a sound. As a former Coast Guard rescue swimmer, I wasn’t surprised at all by this story. Drowning is almost always a deceptively quiet event. The waving, splashing, and yelling that dramatic conditioning (television) prepares us to look for, is rarely seen in real life.

 

The Instinctive Drowning Response – so named by Francesco A. Pia, Ph.D.,  is what people do to avoid actual or perceived suffocation in the water.  And it does not look like most people expect.  There is very little splashing, no waving, and no yelling or calls for help of any kind.  To get an idea of just how quiet and undramatic from the surface drowning can be, consider this:  It is the number two cause of accidental death in children, age 15 and under (just behind vehicle accidents) – of the approximately 750 children who will drown next year, about 375 of them will do so within 25 yards of a parent or other adult.  In ten percent of those drownings, the adult will actually watch them do it, having no idea it is happening (source: CDC).  Drowning does not look like drowning – Dr. Pia, in an article in the Coast Guard’s On Scene Magazine, described the instinctive drowning response like this:

 

1. Except in rare circumstances, drowning people are physiologically unable to call out for help. Th e respiratory system was designed for breathing. Speech is the secondary or overlaid function. Breathing must be fulfilled, before speech occurs.
2. Drowning people’s mouths alternately sink below and reappear above the surface of the water. The mouths of drowning people are not above the surface of the water long enough for them to exhale, inhale, and call out for help. When the drowning people’s mouths are above the surface, they exhale and inhale quickly as their mouths start to sink below the surface of the water.
3. Drowning people cannot wave for help. Nature instinctively forces them to extend their arms laterally and press down on the water’s surface. Pressing down on the surface of the water, permits drowning people to leverage their bodies so they can lift their mouths out of the water to breathe.
4. Throughout the Instinctive Drowning Response, drowning people cannot voluntarily control their arm movements. Physiologically, drowning people who are struggling on the surface of the water cannot stop drowning and perform voluntary movements such as waving for help, moving toward a rescuer, or reaching out for a piece of rescue equipment.
5. From beginning to end of the Instinctive Drowning Response people’s bodies remain upright in the water, with no evidence of a supporting kick. Unless rescued by a trained lifeguard, these drowning people can only struggle on the surface of the water from 20 to 60 seconds before submersion occurs.

 

(Source: http://www.uscg.mil/hq/cg5/cg534/On%20Scene/OSFall06.pdf)

 

This doesn’t mean that a person that is yelling for help and thrashing isn’t in real trouble – they are experience aquatic distress. Not always present before the instinctive drowning response, aquatic distress doesn’t last long – but unlike true drowning, these victims can still assist in there own rescue.  They can grab lifelines, throw rings, etc.

 

Look for these other signs of drowning when persons are in the water:

 

• Head low in the water, mouth at water level
• Head tilted back with mouth open
• Eyes glassy and empty, unable to focus
• Eyes closed
• Hair over forehead or eyes
• Not using legs – Vertical
• Hyperventilating or gasping
• Trying to swim in a particular direction but not making headway
• Trying to roll over on the back
• Ladder climb, rarely out of the water.

So if a crew member falls overboard and every looks O.K. – don’t be too sure.  Sometimes the most common indication that someone is drowning is that they don’t look like they’re drowning.  They may just look like they are treading water and looking up at the deck.  One  way to be sure?  Ask them: “Are you alright?” If they can answer at all – they probably are.  If they return  a blank stare – you may have less than 30 seconds to get to them.  And parents: children playing in the water make noise. When they get quiet, you get to them and find out why.