You may never launch a real rocket, but you can have fun building one with water!
Steps

Step 1. Prepare 2 x 1.5L plastic bottles

Step 2. Cut one of the bottles into 3 parts
Keep the top and middle.

Step 3. Attach the top of the bottle you cut to the bottom of the intact one

Step 4. Attach the middle part of the bottle you cut to the bottom of the intact one (using electrical tape)

Step 5. Cut out 4 panels of acrylic, which will be the fletchings of the rocket

Step 6. Pour approximately 200ml of water into the bottle

Step 7. Cap the bottle by connecting it to the bicycle pump in order to prepare it for launch

Step 8. Place the rocket on the launch pad

Step 9. Pump the air into the bottle

Step 10. Make sure the atmospheric pressure in the bottle is around 70-75%

Step 11. Prepare to Launch
Advice
- Add soap to increase the time in the air and speed.
- The smaller the nozzle of the rocket, the less resistance to take off and more stability in flight there will be. A larger nozzle, on the other hand, will allow the water to escape faster, allowing the rocket to go higher at faster speed, but remember that it will lose water more quickly.
Warnings
- Stay away from the rocket while pumping the air and immediately after.
- Don't pump too much air into the bottle.
- Handle with care.