A paddling jacket can be a difficult choice to make when getting ready to go out kayaking. The best analogy for how a paddling jacket works is that it is the top half or a dry suit. It will provide a layer of waterproof material between your wetsuit and the outside water. This will keep you from getting random splashes of cold water poured all over you as you kayak and keep your upper torso much warmer. Warm days can mean that you will not need a paddling jacket at all, but as soon as the weather turns cold you are going to greatly appreciate having that layer of protection.
When it get s really cold you can add a sweater or other ways to stay warm in between your wetsuit and drysuit. Choose carefully what sweater you wear though, make sure its one that will still insulate you when wet. Any paddling jacket or dry top will not keep you fully dry if you flip the kayak if you go for a swim. If you need protection to that degree, you need to look into a drysuit.
If you are confused about what a paddling jacket is and what a dry top is, it has to do with their degree of waterproofing. Both jackets have all their seams and cuffs with some sort of seal to protect you from having water pour in, but often times on paddling jackets they are not as thourough or as well protected as they could be. On a dry suit, they have a waterproof zipper as well as a very tight fitting gaskets and seals at every opening, on the neck, bottom, and both wrists. This will keep you totally dry in even the worst conditions. They will however not protect you in event of a swim.
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