There have been a lot of informative posts. Mocke's jacket may be the perfect solution. I like wearable, inflatable PFDs. However, I need to comment regarding Nell's post. It is true that paddling in places like Florida during the summer is very hot. But paddling w/o a shirt is a dangerous solution. I've just been treated for my second case of skin cancer. This last one was a melanoma--the worse kind. Fortunately, I think it is taken care of. My wife is currently undergoing treatment for her 3rd case. None of hers have been a melanoma. Sun--the grim reaper of on-water people--is the culprit.
People, especially young people, do not properly access the risk of skin cancer. Rates of Melanoma are the most rapidly increasing of any cancer. There is no effective treatment once it begins to metastasize. Of course, other skin cancers are nothing to take lightly either. While sun screens offer some protection, to rely on these is very misguided. To begin with there is such a vast selection of sunscreens, all with unclear effectiveness, that it is a crapshoot when trying to get good protection. Secondly, no matter what the SPF factor, sun screens should be reapplied every 2 hrs. They must be applied heavily. In a "day at the beach," you should use approximately 4 oz of sun screen. That gets pretty expensive. So, the best solution is a long sleeve shirt (and hat). Dousing yourself with water can help with the heat. It may not be the best for your surf skier image, but it may save you a lot of grief down the road.