Balancing Boats and Floats

Bob the Boat and Flynn the Float-Plane meet up with the Construction Zerbies, who, with the help of Fran the Ferry, are moving rocks across the lake. Bob and Flynn want to help move rocks. Bob has Strut place a rock on his front, but that just tips him forward. Flynn tries a rock on his back, but that just tips him backward. They both try their sides but that doesn't seem to work either. Zack comes by and shows them how he has his rock right in the middle - where it balances. Bob and Flynn decide to try, try again, this time with rocks right in the middle, where they feel they balance the best. Sure enough, when the rocks are in the right spot Bob and Flynn can carry them across the lake with no problem.