First you need to make your diver. Make a 4-5 brick tall column of Lego bricks, and add some modelling clay to the bottom. This is to ensure your diver remains upright, and is able to sink to the bottom of the bottle. Add enough clay to ensure that the top of the column is just at the water’s surface, and it should be fine. Don’t worry if it sinks at first, as long as it returns to the surface it’ll be fine!
Fill the plastic bottle to the top with water, and pop in your diver. Screw on the cap really tightly, and you’re ready to go!
TOP TIP! Don’t use a bottle with a nozzle you can open to drink through – the next step will get VERY messy VERY quickly.
The top of your diver should be inside the cap of the bottle. Squeeze the bottle, and the diver will sink to the bottom. Release the sides, and the diver will return to the surface!