When you are the goose the pond will drain and you need to collect water to get points. But before the pond has fully drained you can switch to the moose by collecting the red switch element. When you are the moose the pond is overflowing and you collect dirt for points. Then when the pond is about to overflow you can switch back to the goose.

The more element you collect the more the water level will become harder to control. Collect as much earth and water before silly moose or goose lose their homes.