Make a Diving Rainbow DIY

Materials you'll need

• Flexible (bendy) straws
• Colorful paper clips
• Scissors
• Glass or bowl of water
• Large plastic bottle with cap

 

Step-by-step tutorial

Step 1: Cut out just the bendy, accordion section from a flexible straw, leaving a short piece of straw on each side of the bend. Fold it into a "U" shape so both open ends point the same direction.

Step 2: Thread a paper clip through both open ends of the bent straw piece to hold the "U" shape together and trap air inside. This is your diver!

Step 3: Drop your diver into a glass or bowl of water to test it — it should float just barely at the surface. If it sinks right away, remove it and add another paper clip to the loop for more weight. Adjust until it floats with just a tiny bit of the straw poking above the surface.

Step 4: Make as many divers as you'd like using different colored paper clips to create your rainbow set.

Step 5: Fill a large plastic bottle completely to the top with water, then gently drop all your divers in.

Step 6: Screw the cap on tightly. Squeeze the bottle hard and watch your rainbow divers dive to the bottom. Then release your grip and see them shoot back up!

Learn more

This is a classic experiment called a Cartesian diver! Each straw diver traps a small pocket of air inside its curved shape. When you squeeze the bottle, the pressure travels through the water and compresses that trapped air — shrinking it. With the air taking up less space, the diver becomes denser than the surrounding water, so it sinks! Let go and the pressure drops: the air expands again, the diver gets less dense, and up it floats. Submarines work the same way, using special tanks that flood with water to dive and fill with air to rise back up.