As mentioned on the Health Issues page, blood carries body heat from your core into the many capillaries in your hands. Because there is so much blood flowing through your hands, wet cold hands can rob your body of warmth and keep you chilled despite a sprayskirt, fleece jacket, and dry top. A good pair of gloves is the solution, but I've yet to find satisfactory cold-weather paddling gloves. If you have any suggestions, please let me know.
The thing that kills most people in the wilderness is the failure to maintain core body temperature. One of the basic principles of regulating body temperature is layering. While backpacking, I find myself layering up or down throughout the day. But layering up and down is more difficult when sitting in a kayak, hemmed in by a sprayskirt, and rocking with the waves.
My solution to this problem is to wear pull-on arm & leg warmers that cyclists use. These fleece warmers are perfect for Florida's winter climate, where it is very cold in the morning then as the sun rises in midday temperatures soar.
They are much easier to take on and off than a whole jacket and can stored in your deck bag. Arm warmers can even be taken off from underneath a waterproof jacket without taking the jacket off.
For those of you not familiar with cycling gear, let me recommend a brand. Cycling is an extremely expensive sport and unlike backpacking and kayaking, it is harder to find quality, reasonably-priced gear. Pearl Izumi products can be found in national chain stores and are high-quality for the price.