Bottoms of feet cold (drysuit, 39F / 3.9C water)

[FinnMom]

Neophrene socks sound like something would make your feet sweat. Sweaty feet get cold, so maybe you would be warmer without the neophrene socks. Sweaty feetwere always my big problem trying to keep my feet warm when not moving much (ice fishing, deer stand) and wearing very insulated (Eskimo, etc type) boots.

For diving I always wear 2 pairs of hand-knit (thick, loose-knit) wool socks and have insoles in the boots of my drysuit. Removable insoles can provide cushioning and warmth, and also make it much easier to get the inside of the drysuit boot dry.

 

[davehicks]

After 90 minutes in 39F water your feet are going to get cold no mater what you do.

I find this is accelerated when one goes vertical in the water and all the air is squeezed out of your boots. The longer you can remain in a horizontal position the longer you will be warm. But you always have to go vertical the get out of the water and then your feet are going to get cold.

I did add an insole into my integrated drysuit boots which helps a bit after the dive.

 

[Subcooled]

After 90 minutes in 39F water your feet are going to get cold no mater what you do.

- true
- electric heating will help - at a cost
- bigger boots and more wool (actual real wool, not polyamide "wool") may help
- white skin is a deco risk (and painfull)

But you always have to go vertical the get out of the water

For ten seconds?
And then you are out of the water!

 

[Thrutch]

Thanks, all! Some responses:

But curious, how far into a typical 90 minute dive do your feet stay relatively warm?

At about 45 minutes, I start to feel the cold, and it becomes more pronounced on the bottom of my feet when I fin.

It's also worth noting that if you are wearing too much on your feet it can restrict the capillary blood flow and cool your feet down faster. Maybe less is more?

I thought the larger boots would cover this, but you could be right. Might be a vertical squish that's causing the issue. I'll try a thinner, denser wool sock in place of the big thick guys next time.

How old is the BZ400? How many dives and how many times have you washed it?
Which brings me to my second point, if you run your BZ400 smushed you are going to be cold - period. You'll find hundreds of posts here about minimal suit gas. @TSandM used to run her suit crazy squished based on all sorts of internet advice until it finally dawned on her that's why she was freezing. Part of your cold problem might be self-inflicted.

BZ400x is only three months old, not yet washed because of the exact reason you mentioned.

I try not to run squished down, even/especially at the end of a dive when I need to be warm enough to be off gassing, which is why I've added weight to my rig. That's not to say that I'm not running a bit squished without noticing before the cold sets in, just that I try to avoid it. I'll pay more attention to this on my next dive, just in case.

The only way to keep extremities warm is to keep the core warm. That's true above the surface, but it's doubly true underwater thanks to the constriction of blood flow that occurs thanks to the diving reflex.

Undoubtedly part of it. I certainly feel it on the bottom of my feet first, but it's generally as I'm starting to feel the cold throughout, just not as acutely.

Overall, sounds like I'm right on the border of active-heating territory—or maybe right over it. In a month Tahoe should be back in the low 40s again, anyway, so I can switch back to board shorts and a rash guard.

 

[Thrutch]

Here's a draft of a External Heat Wiki, that eventually @rjack321 (who like me spends too much time in cold water) and @tbone1004 (engineering/ocd/textile understanding) will be asked to edit

This is GREAT info. Thanks for passing this along!

 

[Ontwreckdiver]

Maybe you are wearing too many layers of socks causing your feet to sweat and making them to be cold.
I only wear one pair of these socks inside my drysuit boots. https://www.marks.com/en/windriver-...8.html#323648[color]=BLKGRY&323648[size]=7-11

 

[rjack321]

After 90 minutes in 39F water your feet are going to get cold no mater what you do.

You are 100% wrong here.

I've done more than double that, 3.5 hours in 38F water and exited as warm as I started. And I am extremely slow, barely exercise at all, and crazy cold blooded. My O2 consumption on this dive was 0.6L/min which is downright sedate.

My personal outfit:

• DUI CF200 crushed neo suit
• weezle extreme+ undergarment with matching booties
• midweight patagonia capiline tops and bottoms
• thin wool socks that are stretchy and not tight in the foot or ankle
• 50w motorcycle vest run at 60% on a 15ah 11.1V nominal suit heater so ~25watts, i suspect I turned it up to 80% for the last 30mins of deco just sitting there and with the battery running down a bit but I don't honestly recall. As the voltage drops the output at 80% is about 32watts.
• dry gloves with medium weight wool liners
• 8mm X01 hood
• air suit gas
• 18/45 diluent in a kiss sidewinder CCR with a custom 300wh scrubber heater battery
• 18lbs lead in fresh water

It is possible to be comfortable or even "warm" in <5C water for as long as you need to be - assuming you aren't leaking.

 

[rjack321]

I thought the larger boots would cover this, but you could be right. Might be a vertical squish that's causing the issue. I'll try a thinner, denser wool sock in place of the big thick guys next time.

If you have any that are looser that can help too. Some of my socks are noticably tight at the ankles and I definitely avoid those on the coldest dives cause they cause just enough vasoconstriction to make for colder feet.

 

[Valyngar]

What I didn't see here was use of Argon gas as suit gas. It is really warmer, compared to air water feels 2-3 degrees warmer.

 

[Gareth J]

Another vote for the fourth element hotfoot socks + Arctic socks.

As others have said, you need to keep your core warm as well.

In addition, protect your extremities to reduce heat loss. A good hood, and dry gloves.
Keeping warm is about minimising heat loss.