Really Cold Water and Max Obligation Time

[Rick Inman]

As I've been progressing through my technical training this Spring/Summer/Fall, my depths and obligation times have been progressing as well. My dive Saturday was to 200' with a 50 min deco obligation

Around here the water temps are always in the 40's at depth, but during the warmer months, surface temps can be well into the 70's, making for nice warm deco, and a nice safety factor should a major suit failure (flood) occur. However, this Saturday's dive temps were 42F below 150' with a max temp of 52F near the surface. Very soon we won't see temps above the 40's anywhere in the water again until June '07.

It's one thing to have a flood and have to deco in 60-70 degrees, but when the temps drop below 50f, you're talking about getting very sick deco-ing for 30 mins or more.

Where do you all draw the line regarding water temp / obligation time?

 

[cerich]

Hi Rick,

It's a good question that I honestly think comes down to personal risk/benefit. I've done deco in the low 40's that had a drysuit flood occured things would get very bad very quick.

Another thing to consider, if you get that cold your body is doing an HORRIBLE job of deco, even following the schedule exactly. Given the poor deco and serious risk from the cold you may be better off getting out of the water and treating the DCS.

Unfortunatly there is no clear cut answer...

 

[Meng_Tze]

No line drawn.......

It is all looked at individually. If I feel super, I will do the dive, hang the deco and bite my time, maybe add some extra cons. for temp.. If not, or can not be bothered, I will not and wait until the waters warm up.

Dont plan on a suit flood, if that happens, recalculate maybe take the risk of a hit....

 

[rjack321]

I'm not doing 50 mins of deco (more like ~25 mins), but one thing you might consider is running a super aggressive profile. Like what is the bare minimum you could theoretically do and come out ok? (i.e. like straight Buhlmann) Then think about how your suit flood scenario could or could not run at least an super aggressive deco in an emergency.

If I were doing more serious profiles I think I would scale back my ambitions in the winter a little.

 

[cerich]

I'm not doing 50 mins of deco (more like ~25 mins), but one thing you might consider is running a super aggressive profile. Like what is the bare minimum you could theoretically do and come out ok? (i.e. like straight Buhlmann) Then think about how your suit flood scenario could or could not run at least an super aggressive deco in an emergency.

If I were doing more serious profiles I think I would scale back my ambitions in the winter a little.

I don't follow, a straight Buhlmann will give you longer deco time than most more recent algorithms (RGBM, VPM etc).

You don't want aggressive in cold, you body literally can't handle it.

 

[rjack321]

Maybe, I don't have all the ways to compare. I wasn't suggesting actually using a super aggressive profile. Its just a baseline against which to compare your obligations. How far could you push things and at least "maybe" come out ok? If the alternative is freezing to death.

Otherwise, minus the suit flood, I'd be padding the deco in 42F water. Since my extremeties are likely to be quite cold.

Rick do you have a dry hood or at least a super warm wet hood?

 

[Rick Inman]

Rick do you have a dry hood or at least a super warm wet hood?

Superwarm wet hood. Hands and feet are the first to go, but on Saturday's 80min dive I never got cold (did swim around a bit on the 20' to keep the blood flowing).

 

[rjack321]

I have a 12mm wet hood, but even with that I don't think I could stand 80mins.

 

[matt_unique]

One season I did a Spring deco dive to 150'. I anticipated the cold during the stops (temps were in the low 40's). Even with a very short 15 minute deco obligation (70% Nitrox) my hands and feet were like ice when I surfaced. From that point on I decided to wear chemical heat packs in my boots and gloves when water temps are below 48 degrees or so. I think it's personal tolerance from that point.

During the late summer and fall the nice blast of warmth for deco above the thermoclines is nice. Ahhhhhhhh

--Matt

 

[fire_diver]

I don't follow, a straight Buhlmann will give you longer deco time than most more recent algorithms (RGBM, VPM etc).

You don't want aggressive in cold, you body literally can't handle it.

I think we have lost sight of the original question.

Ricks not asking about getting out of the water fast becuase you're uncomfortable. He's asking about getting out of the water because you will die from hypothermia if you don't.

I must admit it's a question I haven't thought of before. I'm just now contemplating buying a drysuit. I dive 40's-50's water all the time in my 7mm, but I don't have huge deco obligations. If I start to get cold, I can always ascend. If I get to take my adv nitrox/deco class next year that will all change.

Back to the question.... I think that DAN (or an equivilent MD) could provide some good insight to this. The time spent exposed to cold water will become fatal, but so will DCS. I think that some time tables for exposer to water temps probably exist somewhere. Beyond those limits, you would have to surface and try to get to a chamber ASAP.

FD