Easy Way to Estimate Amount of Undergarments to be Comfortable in a Given Water Temp?

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Great Lakes Mermaid
ScubaBoard Supporter
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Great Lakes
# of dives
200 - 499
I have a trilam suit.

For 50F/10C water last weekend, I had a thin polypro base layer, Thermolution heated vest, Fourth Element X-Core fleece vest, then DUI DuoTherm 300 thick fleece undersuit. On feet, silk liners and Fourth Element Hot Foot socks. I use Fourth Element fleece liners under my Kubi dry gloves.

The Hot Foot Socks are new. I had been using FE Arctic socks for some years. I’d wear medium weight merino wool socks underneath. The Hot Foot socks are much warmer. I found the silk liners in my sock drawer. The Hot Foot socks fit too closely to allow the wool socks under.

For FL cave diving in 72F/22C water, polypro base layer under merino wool, and X-Core vest.


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# of dives
200 - 499
here is the 4th element undergarment layering guide, I learned a lot from it. I like the 4th element undergarments.
for cold water i use J2 wicking layer> Therma-john thermal underwear,> 4th element artic onesie
medium cold - J2>artic
warm water - J2> old worn out DUI artic onesie

my old DUI onesie was perfect in Yucatan caves because it has almost no thermal qualities left


  • temperature-layering-guide.pdf
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# of dives
100 - 199
I use 2 garments.
one for above 20c, and one for below.

I use an Avatar undersuit, 450g teddy fleece, which has served me well for anything. 4C no problems. I get cold on my hands and head way before on my body. I've used it for ice diving, and winter diving for the whole year.

In the spring, summer, and warmeer temperatures, I use a cheapo 150g fleece shirt and underpants form decathlon. they work great.

What I really liked and what made a massive change for me are drygloves and a good 7mm hood. I use the bare 7mm dry hood which has a ton of glideskin and it keeps my head super warm.

Keep in mind their chart is way off, I usually weat an XL, and based on their chart I'm an XL, but the suit is huge. So maybe size down on their website.

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