Until I bought my drysuit...I dove cold water with a 7mm, a 5mm hooded vest, and 3mm gloves...I was doing it so I could dive year round...now I prefer using my drysuit. The water warms up after the initial shock to the body; however, if the water is that cold it usually means the air is pretty close and getting out wet and cold means staying cold for a bit without a good fire going. I recommend doing it atleast once.