Being from Texas, I'm not by any means an authiority on the subject of cold water. But here are my opinions:



A wet suit allows water to enter the suit. The water is trapped between the neoprene and your body, and is then warmed by your body. The neoprene and trapped water act as insulation. (purely my definition, flame suit is on). A wet suit does not provide protection for extreme cold temperatures (my guess, less than 50 degrees).



A dry suit does not allow water to enter the suit. The suit acts as insulation. A dry suit provides protection for colder water and, with extra undergarments, extremely cold temperatures.



Here in Texas, our average water temp are in the high 50's and our air temps are in the 40-60 range.



I've been using different compinations of a 3mm wet suit, Gill Breathable Spray top, Gill Breathable Spray bottoms, neoprene booties and Gloves. Depending on conditions (the colder it gets), I'll layer the wet suit and spray suit.



As stated earlier, coming from Southeast Texas, I'm definately not a great source for this type of information. Just my '$0.02'.