The simplest way to make technology from waste products is as follows:

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

2. Buckle the bottom on the table, and use a marker to draw the propeller on the raised part of the bottom.

3. Cut off the part where the propeller was drawn to get a rather special propeller.

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

5. Then drill an offset hole in the propeller to lock the paper clip.

6. Drill holes in the center of the bottle cap.

7. Pull a paper clip apart and keep a hook.

8. String the bottle cap, beads and propeller together. Use small beads between the propeller and cap to reduce friction.

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

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

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

12. Drill a hole on the edge as well, as shown in the picture below.

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

14. Take out a piece of wire and make a hook, hook the rubber band, put it into the plastic bottle, and let the rubber band hook the paper clip hook at the bottom of the bottle.

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

16. Use two rubber bands around the bottle to secure two ice cream sticks as stabilizers, acting as "fins" to ensure the body remains still.

17. The simple submarine is completed. If the bottle is filled with air, the propeller will be above the water. If the bottle is filled with water, it will become heavy and sink and cannot move.

Try different amounts of water in the bottle, try to make the propeller just submerged in the water, rotate the rubber band of the propeller, and you can move forward like a real submarine.