I had major problems with mice getting my RV and also tried the water bucket with and ramp up to it. Worked pretty good and the raccoons would clean it out for me most of the time. Mice were still getting in my RV when someone told to put fresh dryer sheets (like Bounce) in all the drawers, closets, behind the couches, in all compartments, behind anything you can reach. They hate the smell or something and I've had no mice in there as long as I put the sheets out. Refresh them once a year and it stays good. One word of caution, dryer sheets are very flammable! I would keep them away from ANY sources of ignition.
I like this method for we travel with our pets and using D-Con is to risky for them.