Instead of using a dowel or ruler for a fishing pole, try using a plastic shower ring. The child can hold the ring, which has the string and magnet tied to it, and use it for fishing, just like a pole. This was also easier to manipulate for some of my children than a traditional pole. First put down a sheet of blue bulletin board paper. Children can make rocks to go around it by covering boxes with paper bag paper and sponge painting them black.
Children can also make stuffy fish to put in the pond.
Add magnets to them and the children can fish for them using poles attached to magnets on a string. Also add ducks to the pond by coping duck pattern and attaching them to coffee cans covered with green paper. For a science activity with this activity have children predict and experiment with different magnets to see which one is the strongest to put on their fish. Children can graph their answers to see which magnet is the strongest. The Perpetual Preschool.