Cold while diving

[Marie13]

double post

 

[Marie13]

double post

 

[Scraps]

There's a fair amount of distance between feeling cold or chilled and having mild hypothermia.

Obviously, if you run through the symptoms of mild hypothermia--shivering, mental confusion--you know you don't want that going on underwater.

So I think your instructor was talking about something else.

Among the body's first responses when it is chilled--again, we're not talking hypothermia--is to increase the rate of metabolism. Here I am out of my depth scientifically and speaking just from experience and perception, but I notice my air consumption increases when I'm chilly. So, although breathing gets slower and shallower during hypothermia, I think it gets faster in the early stages of the body's response to being cold. (I invite better informed members to correct me if I'm wrong here--I didn't even read it on wikipedia.)

If increased metabolism doesn't do the trick, the body's next response is to create an urge to eat and increase activity to ramp up production of heat. In a diving context, this will make it harder to relax and conduct your dive with smooth, slow movements.

Plus, by this time, you are now thinking about being uncomfortable, which can distract from your execution of your dive plan and your overall situational awareness.

So before you experience any symptoms of hypothermia, being cold can negatively affect your diving. This may be what your instructor was getting at.

 

[TMHeimer]

I notice my increased air consumption in cold water. A noticeable difference in how long a tank lasts. It may distract from the dive plan because you are thinking of how far you can go based on how cold you are. You may be right about what the instructor meant.

 

[kelemvor]

I was always told that being cold is a problem in its-self. It certainly makes a dive less enjoyable for me. To that end I got a drysuit for spring diving (72f/22c water). Hypothermia means you ignored the cold problem for way too long.

On the other hand, we don't have what you northerners call "cold" water down here. It may be a matter of perspective.

 

[Esprise Me]

Among the body's first responses when it is chilled--again, we're not talking hypothermia--is to increase the rate of metabolism. Here I am out of my depth scientifically and speaking just from experience and perception, but I notice my air consumption increases when I'm chilly. So, although breathing gets slower and shallower during hypothermia, I think it gets faster in the early stages of the body's response to being cold. (I invite better informed members to correct me if I'm wrong here--I didn't even read it on wikipedia.)

This is a good point. My RMV diving in local waters, where I'm comfortable emotionally but perpetually slightly chilled, typically ranges from about .5 to .8 cf/min. I rarely get it below .5 in water cooler than 70 degrees, but in Turks & Caicos, where the water was 80 degrees, my RMV on at least half of my dives was below .5. I was wearing the same wetsuit with the same amount of weight I use at home, and the handful of times I've broken the .5 barrier at home I was in a drysuit--more weight and drag, but toasty warm.

It's often said that women have a better SAC rate than men, and this has any number of possible causes, but my money is on men's higher metabolism rather than greater size. I'm a woman but I'm just under 5'10, which makes me slightly taller than the average American man. I may be a bit less muscular but I'm no weakling, and in terms of total body mass I'm pretty much on par with a lot of guys. Yet I get cold more easily, and I require a bit less air than most guys my size. (Some can beat me on skill, but few can beat my sitting-on-the-couch RMV of .33 cf/min.)

I have an acquaintance who is trans and blogged about his experience taking testosterone. It was a fascinating read, but one entry that still sticks in my mind is about how hot he felt all the time since starting T. Before he began hormone therapy, he was into crossfit, so he was already really buff; he didn't get noticeably bigger (and certainly no taller) as a result of the hormones. And he had always dressed in masculine clothes, so his wardrobe didn't change. But he went from needing a sweater at the office to desperately wanting to unbutton his shirt. It's too bad he's not a diver; I'd love to hear what happened to his SAC rate!

 

[Marie13]

My usual RMV in drysuit, heavy undies, and steel doubles in 45F water is .6. The lowest I’ve ever had was .54, same equipment, same water temp, on a very relaxed quarry dive.

I tend towards running hot. I’ve always hated being hot in the summer. A/C is at 68-70F. Now with the hot flashes, it’s even worse.

 

[thewalrus]

I'm almost always a little cool when I dive. I did a whole year off Vancouver Island in a 9mm wet suit. That wasn't fun, or smart, and I definitely used a lot more air diving that way. Now that I have a dry suit, and decent thermals, I might get a touch of a chill when the water is around 7 - 8 C. But once it goes beyond that I'm actually quite comfortable. Interestingly, just yesterday, my dive felt almost tropical in my drysuit. Bordering on warm. I mentioned this to my buddy on the surface, we checked our computers and found out that the average water temperature had, indeed, risen to a balmy 9 C!

 

[Frackingawesome]

When i am in bonaire, no wet suit and just relaxing mine is around .4-.45 The last few cold dives i have done in a drysuit and very anxious as there was a bunch of new gear, switched to doubles and was fold i was almost at a .8

 

[Frackingawesome]

If increased metabolism doesn't do the trick, the body's next response is to create an urge to eat and increase activity to ramp up production of heat

That would explain why i am so hungry after a dive. Some times i feel like i could eat everything in sight!