The photo shows a tube with a bit of peanut butter on the end. When the mouse crawls through to get it the tube will unbalance and fall into the bucket of water. It will tire itself out and eventually drown. I've seen mouse outsmart many other trap designs, but this one has been very successful, and it's simple.
Many mouse trap designs are filthy mechanisms, leaving a mess or worse, leaving you to do the job yourself. usually relocating a rodent means it will just come back inside again.