down4fun:Told you I am whimpy. Actually I am pretty athletic and lack much natural insulation.
Thanksfor the link I will definitely check it out.
Don't go too much by what other people are comfortable diving in. I find that it is a multitude of factors on whether you or the other person gets cold diving. Body shape can make a big difference. A tall and skinny diver will lose more body heat compared to a short thick diver (larger surface area). The other factors are metabolism and % of body fat and how deep you are diving (neoprene will crush the deeper you go and will permanently be that way after a number of dives).
You say you are very athletic. If you are really fit you will definitely have a slower metabolism because you have trained your body to be more efficient.
I dive in seattle where it is 45f winter and 55f summer, so I have a drysuit. I have just purchased a Weezle extreme because I am getting too cold during the winter dives to do two dives much less being comfortable at the end of the first dive. I hope it works.
I also dive tropical in Asia where the temps are 81-83F or 26-28C. I wear a 3mm full suit and after doing 3 dives a day for 5 days, I just am getting chilled down and am cold at the end of the dives. These are usually 60 minute dives at 65ft or deeper. Even when I ease up to 2 dives a day I'm chilled in the water toward the end of the dives.
I'm no lightweight and am 6ft and 200 pounds. Maybe it is my metabilism. I work out but my body fat isn't that low I don't think. My wetsuit is a 3mm O'Neil. Now that I have about 90 dives in this suit it is pretty compressed. A dive shop in the Phillipines had some new 3mm suits hanging up and I swear they were thicker than my 3mm was new. I will actually purchase a 5mm for any future warm water diving and am looking at the Henderson line of suits. All the instructors I dive with in the tropics wear 5mm because they dive a lot and they have gotten acclimatized to the warm surface temps.
Remember whatever neoprene suit you do get will be compressed after a fair number of dives (how many I don't know - was told about 30 at one time) so think of what thickness the suit will have after those first dives.
Sorry for the long post but I have learned not to depend on other divers ideas of cold and what to wear because of all of the above.
Jason