Animal Recycling is the seventh mission in WorldBuilder.
Pick up the plans for the Fish and the Duck. Build a Snail, move it near the river, take it apart, then build a Fish (do not worry about the whirlpools; they are nothing more than a minor nuisance, and can easily be navigated around). Move the Fish near the yellow bricks, then take it apart, build a Duck, and move it to the goal.
Move the Duck near the trees on the side where the Buggy is located, then take it apart and rebuild it near the goal.