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

[Thrutch]

I'm trying to dial in my exposure protection for winter Lake Tahoe diving. It gets down to (and is currently) 39F, pretty much from the surface on down. I've taken a number of steps to boost my thermal protection and have successfully done 90 minute dives at this temp without getting too chilly. BUT the bottoms of feet get cold right where my insulation compresses when I'm frog kicking. I'm experimenting with some cheap insoles stuffed into my socks, but I'm curious if anyone has advice in this area.

My setup:

• Trilam drysuit
• Expedition weight baselayer top and bottom
• Santi BZ400x undergarment
• Smartwool expedition weight socks
• Fourth Element Arctic socks
• Drysuit has 3mm compressed neoprene socks
• Size 13 NRS paddle boots (up two sizes from my normal boots to accommodate the extra insulation)
• KUBI dry gloves
• Wool + 40g Thinsulate gloves I found on Amazon (these work really well)
• Waterproof 10mm hood (the sweet orange one)

I'm also diving double steel 100s on an SS backplate with V weights and an extra five pounder so I can stay down at the end of the dive for deco obligations without having to completely empty my suit and subsequently freeze.

TL;DR. I'm diving in cold water and frog kicking while doing so, which makes the bottom of my feet get cold. Any tips?

 

[formernuke]

Following, mine get cold when I get out of water. It's better now that I'm using rockboots again.

 

[grantctobin]

Feet get cold for two reasons (three if you count misc medical things like reynaud's). Cold core (body moves heat towards things it wants to protect) or poor circulation (body can't put warmth in places blood isn't actively going in and out of).

I do think there's a point in warmth/duration where safety increases for a slightly heavier suit gas:wing ratio and you're about there.

Your options, assuming you're already optimizing caloric intake, pre dive ritual, etc, (imo) in order of decreasing value per warmth unit, include:

-FE XCore vest or similar
-12+ mm Otter Bay custom hood (get one of these)
-Heated vest
-Heated socks+gloves
-Heated BZ400x
-Neo suit
-CCR (warmer gas)

At a certain point in sub 40 degree water (and with deco), there's little choice but to add external heat. You're also approaching exceedingly poor offgassing, especially in times of year without thermocline.

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

 

[ontdiver]

It sounds like you have checked all the boxes. But curious, how far into a typical 90 minute dive do your feet stay relatively warm?

 

[asher102]

What about trying different sock combos? I have been liking the Fourth Element Hotfoot socks.

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?

Other than those 2, active heat?

 

[rjack321]

How old is the BZ400? How many dives and how many times have you washed it?

I despise thinsulate because it breaks down way too fast for me. I use my older 400gm thinsulates in FL because anything colder than 65F with them is cold.

I am a big fan of the weezle extreme+. I have one still in use that is 12 years old with maybe 650 dives on it. Its not as warm as it used to be but definitely still works. Expect to add 2 to 3 lbs going from 400 gram thinsulate to a weezle. That is the difference in loft, that's at least 1L of extra insulating air in your suit. The weezle booties are also shockingly good despite feeling flimsy and vastly better than the 4th element. Those could be a fairly cheap change if your feet are the only real cold spot you have.

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.

 

[wnissen]

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. Does make me wonder, would your feet be warmer if you switched to a full-face mask?

 

[rjack321]

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. Does make me wonder, would your feet be warmer if you switched to a full-face mask?

The OP says he has deco obligations. FFM is a very poor choice for deco diving with a buddy for a myriad of reasons.

 

[wetb4igetinthewater]

Since you mention the bottom of your feet, I've put some alpaca wool liners in the bottom of my boots. However, the integrated boots on my DUI dry suit are relatively thin as compared to my Northern Diver neoprene dry suit. It helps a little.

 

[happy-diver]

Fashion yourself some fake sheepskin insoles