I've spent several years hunting Canyon Ferry, there are several very good places to hunt.
On the north side of Canyon Ferry there are three ponds with some very nice islands to hunt off of. Take highway 12 to about 2 miles outside of Townsend and turn to the left and there are several access roads that will lead you to the three ponds. Don't bother hunting pond one, it's worthless. Although you can sit on the dyck and pass shoot ducks flying arcross the lake it's self.
Islands two and three are best, and with moderatly shallow water, any of the islands can be accessed with waders (a jon boat is better)
There are several spots on highway 12 leading to Helena on the south side of the lake. My personal favorites are not but a mile or two down the road from the Missouri River Bridge.
Hope that helps,
PM me if you need more info, I can even e-mail ya a couple of Sat photos if you'd like.
Lord......let me be as good a hunter as my dog thinks I am....amen