Really Cold Water and Max Obligation Time

[electric_diver]

My answer is : it depends. There are so many things to consider: deco time, water temp, surface conditions, available support (shelter and O2 availability on surface) etc

However I think I'd choose mild hypothermia over probable DCS as a general guide. I'll stay in the water until I stopped shivering. The cessation of shivering is an indictor that hypothermia has progressed beyond mild. You definately want to be out of the water before you become seriously impaired mentally and physically by the cold.

I think it is probably wisest to limit your deco obligations when diving in very cold water.

 

[limeyx]

My answer is : it depends. There are so many things to consider: deco time, water temp, surface conditions, available support (shelter and O2 availability on surface) etc

However I think I'd choose mild hypothermia over probable DCS as a general guide. I'll stay in the water until I stopped shivering. The cessation of shivering is an indictor that hypothermia has progressed beyond mild. You definately want to be out of the water before you become seriously impaired mentally and physically by the cold.

I think it is probably wisest to limit your deco obligations when diving in very cold water.

Sadly, I think "it depends" is about the best anyone is going to come up with.

I think as others have said, this is a good reason to limit exposure (GUE for instance recommends total exposure of 90 mins in the ocean, and a reduction for really cold water).

Also a good argument for a good drysuit and a good set of thinsulate undergarments.

I think the point RJack was getting at is that you run a profile something like "OMG" deco (OMG = Oh My God) -- this is the absolute minimum deco you think you need to do and have a good chance at no permanent DCS effects.

Then you do your regular deco plan. If you suffer a leak/failure, you can then potentialy convert to the OMG deco in the absolute worst case.

Also maybe a good reason to push as much deco deeper as you can since deeper=earlier in the dive generally, so more chance of getting the deco done, but also (again in theory) more chance of keeping bubbles small and avoiding a typeII hit if you have to blow off the shallow deco.

I know of people locally who have essentially blown off the shallow 12-15 mins of deco on a Tech1 dive (on 50%) -- so approx 1/2 the deco and been fine (but then there are probably people who did way more than the required deco and got bent).

Also one very well known local diver once told me he cut a 20 foot stop short by 20 mins+ because he had to do a "number 2" -- and walked away from the dive.

 

[Irene]

Its rare for a drysuit to "suddenly flood". Its more likely that you'd feel a spot thats much colder than the rest and wonder to yourself if thats a leak. As that spot grows, you know that it is. End the dive. A sudden flood would more likely happen if you burped the neck. Adust and end the dive. Sure, you'll be very wet somewhere, but probably not as wet as total immersion. End the dive.

In most cases, I beleive that you'd have some warning about your drysuit failing long before you racked up a large deco obligation.

Once you realize that your dry suit is failing, you end the dive.

 

[1_T_Submariner]

Any thoughts on wearing a Wetsuit as underwear for your dry suit? I'm kind of new to drysuits so this may sound off the wall.

 

[matt_unique]

That would be interesting for sure but would likely cause problems with the neck and/or wrist seals for one. You would also loose mobility. Not to mention the amount of lead you would need to carry.

In terms of the drysuit flood, it would take a slice across the entire front of the suit for example to cause a "major" failure. The above summary of the flood experience is right on. I once dove in 33 degree water with a hole in my suit. I realized it the moment I submerged, surfaced to inspect, then dove for as long as I was reasonably comfortable. The right thermals will do a good job to 'wic' the water away from your skin until it become saturated. I lasted for 15 minutes with water coming in my arm until I needed to surface.

--Matt

 

[Rick Inman]

Any thoughts on wearing a Wetsuit as underwear for your dry suit? I'm kind of new to drysuits so this may sound off the wall.

Good thought, but neoprene would not make good insulation under a drysuit. Neoprene uses a layer of water between the suit and your skin - warmed by your body heat - as insulation. A drysuit uses air (or argon) in a fabric to keep you warm. Then there is the bulk issue, which would be motion prohibitive and uncomfortable.

It would really be mixing two different design ideas, AFAIK.

 

[Falco]

I don't know if this is a valid idea, but you could use heated undergarments for your deco. I've tried heated gloves before on a dive (I get cold hands quickly) and it was like day and night. No more loss of dexterity by using another pair of gloves under my drygloves (the heated gloves are maybe 1-2mm thick).

 

[MikeFerrara]

We shorten out run times in cold water. I've had several dry suit floods where I got pretty wet. Good under clothes will provide some insulation even when wet and most floods aren't mass floods as in the suit is torn wide open.

Still cold water can mean getting cold even if your suit doesn't flood and water in your suit is going to mean getting cold quicker. Like I said, we limit our run time in cold water.

In 55 deg F water we limit deco to 70 min or so (calculated conservatively). We'll stretch that some if our 20 ft stop is outside the cave where it's warmer in the summer. Spring time in the grat lakes where it's 40 deg top to bottom we keep run time to 60 min or so but in open water we're usually doing shorter dives anyway.

The guys doing real long dives in cold water are using heated underclothes but it's expensive stuff. the setups I've seen used scooter tubes for batery packs and they rigged them like deco bottles. In a cave, they drop them and pick them up for deco on the way back. Slick stuff but I'm happy just doing shorter dives.

 

[limeyx]

Its rare for a drysuit to "suddenly flood". Its more likely that you'd feel a spot thats much colder than the rest and wonder to yourself if thats a leak. As that spot grows, you know that it is. End the dive. A sudden flood would more likely happen if you burped the neck. Adust and end the dive. Sure, you'll be very wet somewhere, but probably not as wet as total immersion. End the dive.

In most cases, I beleive that you'd have some warning about your drysuit failing long before you racked up a large deco obligation.

Once you realize that your dry suit is failing, you end the dive.

It's also unlikely to go OOA, but we still try to account for those rare cases.
Here I think it's a "Very unlikely to happen, but could be really serious if it did" kind of case that's worth considering.

 

[lundysd]

As someone who has done an hour dive in Puget Sound (55 max temp) in a 3 mil wetsuit and 1mil gloves, I can assure you -- your body can take more than you think. I did stop shivering about 40 minutes in, and did come up mildly hypothermic, and yes it was stupid, but if I was in mandatory deco I'd do it again. What can I say -- I really wanted to dive

Re: wetsuit as undergarment. It sucks. You have no flexibility, and although it's better than nothing, the thermal properties really don't help much. I bought an el-cheapo seasoft undergarment and it works substantially better (now I have a Weezle and it's amazing).

Keep in mind that even a wet drysuit will also provide thermal protection -- especially in an undergarment like a Weezle, which remains an insulator even when wet. A fully soaked drysuit with a good undergarment will always be better than a thin wetsuit or nothing at all.