First, let's build the circuit: power + light trigger + wire + fan + wire + long led + long led + buzzer. The light trigger will be located inside of the lower jaw. The fan, the two long leds and the buzzer sit inside the upper jaw. The fan and the long leds will act as eyes.
To make shark’s body, cut a large piece of cardboard into a square shape. Then with a pencil, divide the square into four small squares of the same size. Cut out one piece of this small square. This going to be the lower mouth and the other three pieces are upper mouth.
Now you have one small square and one big ‘L’shape. Give your shark some sharp teeth by making zigzag edges on two continuing edges of the small square and on the two inner edges of the big ‘L’shape.
Bend each of the cardboard pieces half, along the symmetric centerline.
Now for the tricky part. You are going to connect the two parts of the jaw together with a hinge made of cardboard. To do that, you need a piece of cardboard that is the same length as the the initial big square you cut. Make its width be ⅓ of its length. With this strip of cardboard, measure how long the shark’s upper lip is, and mark it on the board. Then measure how long the shark’s lower lip is, and mark it on the strip from the other end. Now you have a board with three sections. The longest section is the upper side of the mouth. Cut it down to a triangular shape. The section on the other end of the board will be lower mouth. Cut it into a triangular shape as well, but this time, make it thinner and more pointy so that the lower jaw goes inside of the upper jaw when the shark closes his mouth. Otherwise, the teeth on the upper and lower side interfere each other and the shark can not close his mouth, making it so he is unable to eat fish.
Make eye holes using a box cutter. Then make a small hole (about half inch of diameter) in the bottom of the mouth. The light trigger will sit behind this hole.
Put all three pieces together. We used tape but hot glue is also fine. Keep in mind that hot glue is literally ‘hot’.
We are almost there! Be creative and paint your shark as crazy as you like. Painting is a fun and easy way to decorate
Make some handles out of cardboard and tape one on the bottom of the mouth and one on the top of the mouth.
Place your circuit into the shark’s head. Make sure you place the light trigger directly below the small hole in the mouth so your shark is easily able to sense the fish that land in its mouth. Place the fan behind one eye hole and the long leds behind the other eye. Make/find some materials for eyeballs to be more expressive. We used a piece of paper with a spiral drawn on it and a foam ball.
Now, throw fish into your sharks mouth! When a fish lands in the mouth and covers the light trigger, your shark will activate.