1. Take a coke plastic bottle and cut off the bottom with a knife.

2. Buckle the bottom on the desktop and draw the propeller on the raised part of the bottom with a marker.

3. Cut off the propeller to get a special propeller.

4. Then drill a hole in the middle of the propeller.

5. Then drill an offset hole on the propeller and lock the paper clip.

6. Drill a hole in the center of the bottle cap.

7. Open a paper clip and keep a hook.

8. String the bottle cap, beads and propeller, and use beads between propeller and cover to reduce friction.

9. There should be a hook inside the bottle cap.

10. Insert the extra paper clip into the hole on the edge of the propeller.

1 1. Take out another plastic bottle and drill a hole in the center of the bottom.

12. Also drill a hole at the edge, as shown in the figure below.

13. Take another paper clip, pull it out and insert it into the hole in the middle of the bottle bottom, make a hook inside, and insert the other end into the hole on the edge to lock it.

14, take out a wire to make a hook, hook the rubber band, put your hand into the plastic bottle, and let the rubber band hook the paper clip hook at the bottom of the bottle.

15, then pull the rubber band out of the bottle mouth, hook it with the hook on the bottle cap, and tighten the bottle cap.

16. Fix two ice cream sticks around the bottle with two rubber bands as stabilizers and act as "fins" to ensure that the body remains still.

17. A simple submarine has been made. If the bottle is filled with air, the propeller will emerge from the water. If the bottle is filled with water, it will become heavy, sink and cannot move.

Test different amounts of water in a bottle, try to make the propeller just sink into the water, and rotate the rubber band of the propeller to move forward like a real submarine.