I did some shallow diving without wetsuit in California in 64 degree water. It was very uncomfortable for me. After about 5 minutes I came out blue (fingernails were blue) and shivering. Others were cold, but okay with it. Others wouldn’t even go in the water.
It’s a personal thing.
Most of the scuba diving industry refers to cold water diving as below 60F. Due to the extreme heat loss and potential equipment issues, once you start getting in <60F water these factors really start playing a role.
If you’re talking about personal comfort, I always say, cold is relative to what you’re wearing. I’ve dived 15°C in a two-piece semi-dry plus hood, but that was uncomfortable. Now I use a drysuit for anything under 20°C, and a two-piece with hood for anything up to about 25°C. Divers with lower surface:volume ratios (i.e. more natural insulation!) than me might think that a bit wimpy, but I’d rather be warm than not.
If you’re talking about the risks of regulator freeze-up, I would say ‘cold’ is anything under about 5°C (41°F), when the cooling effect of depressurising air, added to the low water temperature, might be enough to cause ice to form in/around the moving parts of your second stage. (If you’re diving in water that cold, your first stage should be environmentally-sealed.)
I did some shallow diving without wetsuit in California in 64 degree water. It was very uncomfortable for me. After about 5 minutes I came out blue (fingernails were blue) and shivering. Others were cold, but okay with it. Others wouldn’t even go in the water.
It’s a personal thing.
Most of the scuba diving industry refers to cold water diving as below 60F. Due to the extreme heat loss and potential equipment issues, once you start getting in <60F water these factors really start playing a role.
If you’re talking about personal comfort, I always say, cold is relative to what you’re wearing. I’ve dived 15°C in a two-piece semi-dry plus hood, but that was uncomfortable. Now I use a drysuit for anything under 20°C, and a two-piece with hood for anything up to about 25°C. Divers with lower surface:volume ratios (i.e. more natural insulation!) than me might think that a bit wimpy, but I’d rather be warm than not.
If you’re talking about the risks of regulator freeze-up, I would say ‘cold’ is anything under about 5°C (41°F), when the cooling effect of depressurising air, added to the low water temperature, might be enough to cause ice to form in/around the moving parts of your second stage. (If you’re diving in water that cold, your first stage should be environmentally-sealed.)