Mice can jump over the gap, reach the cheese, and run about to float up.
The shaman can build a red-anchored big plank over the gap between the water and the right platform, and then yellow-anchor a small plank to the left end of the big plank. This helps mice get out of the water.
Another method is to place a balloon under the water container and wait until at least three mice are on top of it. The balloon will pop, acting like a spirit, pushing the mice up and out of the water.