Really man used to do it all the time when I used to hunt hard. A river works good. Make them swim against current till they get a good work out. Doesnt take long against that current twice a week. I used it when i couldn't get in the woods or a dog was healing pads or something like that. Its one of those something is better than nothing things. Nothing to me compares to running in 100 dog packs every weekend in a big pen. Where you going to field trial at.