🌊 Ocean in a Bottle

What you need

• □A clear plastic bottle with a tight lid (a 16–20 oz water bottle is perfect)
• □Water — enough to fill the bottle about halfway
• □Baby oil or vegetable oil — enough to fill the rest
• □Blue food coloring (2–3 drops)
• □Optional: glitter, tiny shells, a small plastic fish or boat
• □Strong tape or hot glue for sealing the lid

How to make it

1. 1Fill it halfway with waterPour water into the bottle until it's about half full. Leave the rest empty for now — the oil needs room.
2. 2Add the blueDrop in 2–3 drops of blue food coloring. Cap it and swirl until the water is an even ocean blue. Add one more drop if it looks pale, but go slow — dark blue hides the wave.
3. 3Drop in your ocean thingsNow add glitter, tiny shells, or a small plastic fish. Anything light enough to float or drift will move with the wave.
4. 4Pour in the oilFill the rest of the bottle with baby oil or vegetable oil, almost to the very top. Leave just a small air bubble — that bubble is what makes the wave roll.
5. 5Seal the lidScrew the lid on tight, then tape it down or have a grown-up add a ring of hot glue. This is the step people skip and then regret.
6. 6Make wavesLay the bottle on its side and tip it slowly back and forth. The oil and water refuse to mix, so the blue layer rolls like a real wave.

Tips & the science bit

• 💡Why it works: oil is less dense than water and the two don't mix, so they stay in separate layers and slosh against each other.
• 💡Baby oil gives the clearest wave. Vegetable oil works but is slightly yellow.
• 💡Doubles as a calm-down jar — a lot of kids use it for the exact moments Lulu Lilly would notice.
• 💡Classroom version: have each kid bring an empty bottle from home and run it as a density lesson.

Where this craft comes from

The Great Lemonade Strike

This craft appears at the end of Lulu Lilly and the Great Lemonade Strike — a chapter book for ages 6–9 with 58 black-and-white illustrations.

See the book