there is an app for your phone called Marine and water...It has most of the big water bodies in Montana and even some of the medium ones too! $9.99 in the app store and I think they have it for android as well! I just downloaded it last night and spent an hour looking at lakes around Montana, and the more you zoom in the more detail you get! Also marcsmaps.com is a good place if you are willing to wait for shipping!
