I agree with Sean.
While Kokatat gear has a great name, I have found that dry pants always leave in water while swimming, and believe me, I've done lots of swimming.
I've had two pairs of Dry Pants, both crappy Hiko ones and right from the start, long before the waterproofing gave up, the water pissed in at the waist. This even happened on flat water trying out different ways of overlapping the waist seals on the pants and cag.
If you don't fancy splashing out on a dry suit or salopettes just yet, a "good" long john wetsuit, good quality neoprene river booties, and a good dry cag with thermal layers underneath are probably the best option for staying warm this winter.
If you want to stay dry you will need at the minimum salopetts (I've just ordered a pair of Peak Explorer Salopetts) and a good dry cag, or ideally a good quality dry suit.