What's the general guideline for water temp and exposure suit thickness?

[Phocus]

I know people differ, but is there a general rule of thumb for water temp and exposure suit selection? Something to get me started in my selection process.

[OkiMike]

75F+ = 3/2mm wetsuit
For everything else, a drysuit.

(I'm serious).


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You could add a 5mm between 65F and 75F, but with its poor buoyancy characteristics at depth, why bother?

[Banyan]

A 3/2 is overkill in the tropics with its 81F+ temps. You'll want a 0.5-1mm skin just for exposure protection from scrapes, jellyfish, etc. Someone thoroughly acclimatized to the tropics will start getting chilled after 80 min dives or so, and can probably handle up to 2mm suits without too much risk of overheating.

[Dirty-Dog]

There is not, and really cannot be, a "general guidline" for something as totally individual as thermal protection.

Most shops will be renting whatever suit they think is "average" for their waters. See what that is. Now take an honest look at yourself. Do you wear a sweater in the summer? Do you snow ski in a windbreaker? Adjust up or down from the "average" based on that. Err on the side of warmth and then adjust more.

My wife dives the Cenotes in a 5mm full with 5mm hood and booties. She says that's cool but not uncomfortably so. She wears the same 5mm full without the hood on OW dives in 82F water and thinks it's just dandy.
I dive the same cenote in a 3/2 with 3mm hood and booties. And occassionally vent water through my suit. I've done the Cenotes in a 3mm shorty and was fine, but I think you need a bit more scratch protection than shorties offer. On the 82F dives, I'm most likely to be wearing a lycra dive skin.

[Tortuga68]

Warm water: shorty
Temperate: steamer
Cold: drysuit

There ya go

[HowardE]

My guideline (for open circuit scuba)

82 + = 3mm
78-81 = 5mm
73-77 = 7mm
<73 drysuit

But that's me. I don't see any reason to be uncomfortably cold.

[eelnoraa]

I think it also depends on how many dives you are doing, surface weather condition (can you warm up in SI or not). Before I got my drysuit, I was able to do my first dive of the day in 50F water (40min) with a 7mm wetsuit. It gets cold at the end, but nothing unbareable. The 2nd dive of the day soley depend on the SI. If I were beach diving on a hot day, I can still go in for a 2nd dive, but it starts to get uncomfortable and unenjoyable. If I were doing boat dive, I will not want to go back in.

[Nitro91]

I did my ow course in 16C(60F) water with a 7/5mm suit, no hood,gloves or boots and I wasn't that cold, was fine. But my friends who I did it with, same gear were all freezing they said. So I just bought a 5/4mm and hopefully should still be ok for 60F waters lol.

[kozzy]

I have to agree on number of dives in a day also. I pretty much dive dry all year long, not becasue I get cold, I find it more comofortable. in the 1000 Islands, where I dive most, in late july and August, the water temp gets above 75 Degrees F, and on 85 Degree plus days, Ill dive in shorts and a Tshirt. Otherise I might use a 1/2 mil dive skin during those months. Other than that, dry all the way, in warmer monts, I wear lighter undergarments, and i layer up as it gets colder. Really just have to try and see what makes you comfortable..

[drbill]

Whatever you choose, don't listen to me unless your body type, physiology and tolerance for "cold" are equivalent. I dive a 3mm shorty in water above 75 F, a 3/2mm full in water from 62 to 74 F and a 7mm full from 48 to 62 F for single dives. Despite having a "dry" suit, I don't dive water colder than 48-50 F at this time. If I'm doing two or more dives in a day, I modify this. Of course most of my wetsuits are "holy" so that also affects the choice!