Kokotat are a very good brand, I know several people that swear by them
If you are looking for the best of the best... I'd recommend Mustang Survival, for some reason they don't list drysuits under their Recreational section, but have a look under their Military or CoastGuard section for drysuits.
http://www.mustangsurvival.com/produ...gory.php?mc=37
If you are looking at spending long periods of time in them... make sure you get BREATHABLE fabric... ignore people who say that it doesn't work - they are thinking of diving drysuits. The only thing that you need to do is wash it down with freshwater after every outing, to stop the salt crystals from forming.
I think a lot of people in the UK will recommend CrewSaver HyperDry
http://www.crewsaver.co.uk/crewsaver...s/drysuits.htm
Hope that helps,
WMM