Here we are making water bottle rockets!!!! This is something we wanted to build for a while now and we finally did it. And we absolutely loved it! Such a great and easy DIY homemade science project for kids to make while we all #StayHome. Come on, give it a try! How it works: A plastic bottle is usually used in creating a water bottle rocket. It is pressurized with air and water until the pressure becomes high enough to make the water bottle rocket be released and fly high up the air. ... Fins are attached to the bottom of the water bottle rocket to stabilize it and keep its flight straight.