sweaters??? arent they manufactured with a coarse weave that would let water thru even if the material was waterproof.....
I use layers of polar fleece with a light rainjacket over it mostly for the wind protection... a good rain suit is not much more than windbreaker material, but it is waterproof..
you can get heavier rainsuits, but you dont usually need heavier, but warmth underneath is important.
heavier gear IS sometimes good if you are going to be out in severely bad weather for an extended period.
where a sweater would work for you, you can always spray the polar fleece with scotch gaurd or something similar that makes it very water resistant, but if you are getting a lot of spray, then put the rain suit on...
Or... almost all the marine stores sell 300 to 500 dollar insulated bib/jacket combinations or full insulated waterproof coveralls that have a little sailboat insignia sewn into them...
