Mission: Underwater Air Rescue
A diver is trapped beneath the surface with no way back to the top.
Your mission:
build a hidden underwater air cave that keeps them dry and breathing.
Can invisible air stop water from flooding in?
5-12 yrs
Easy
5
min
Stage 2, Stage 3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Professor Picklebottom
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Mission: Underwater Air Rescue
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
Large clear container or tub filled with water
Clear plastic cup or drinking glass
Tissue paper
LEGO diver, toy figure, or paper “message”
Optional: waterproof torch or light
Optional: ping pong ball
Let’s Investigate
1
Diver goes overboard
Your diver is stranded…
and needs an underwater survival cave before the water closes in.
3
The deep dive
Slowly push the glass straight down into the water while keeping it over the diver.
Watch carefully.
The water rises around the outside of the glass…
but something strange happens inside.
5
Slow leak
Slowly tilt the glass sideways underwater.
Watch what escapes first.
2
Build the air cave.
Place the upside-down glass carefully over the diver ball.
Do NOT push it underwater yet.
First:
make your prediction.
Will the water flood the cave?
Will the diver stay dry?
Is the glass really empty?
4
Check the cave
Hold the glass steady underwater and inspect the diver.
Did the underwater cave survive?
6
The flooded cave
Keep tilting the glass until the trapped air escapes completely.
What happens to the diver’s survival cave now?
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Crazy Scientist LAB Learning System™
Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.
We
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LINK to what they already know,
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ACTIVATE curiosity through hands-on discovery
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BUILD understanding that actually sticks.
Have you ever:
hidden under an upside-down pool float?
trapped bubbles underwater in the bath?
wondered how submarines survive underwater?
If water fills everything…
how can air create a hidden survival cave underwater?
Predict:
Can invisible air stop water from entering your underwater cave?
The diver stayed dry.
But HOW?
The cup looked empty…
yet something inside stopped the water from flooding in.
What was trapped inside the cup?
Why did bubbles escape when the cup tilted sideways?
If the trapped air escaped completely, what happened next?
Air is matter.
Even though you cannot see it, air:
takes up space,
has mass,
and creates pressure.
When the cup goes underwater upside-down, the trapped air inside pushes back against the surrounding water. This creates a hidden underwater air cave.
As long as the air stays trapped, water cannot fully enter.
But when the cup tilts, the air escapes as bubbles and the cave floods immediately.
This same science is used in:
diving bells,
submarines,
underwater tunnels,
scuba systems,
and trapped air pockets beneath overturned boats.
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does the shape or size of the cup affect how much water enters the air cave?
What happens if you push the underwater cave deeper and deeper?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Is the glass really empty?
Everyone thinks the glass is empty when you hold it upside down. But it isn't. It's full of air — invisible, but very much there. And before it goes underwater, that air is pressing outward in all directions.
Air has weight. The entire column of atmosphere above you is pushing down on the water in your container. Scientists call this air pressure, and it pushes sideways and upward too — not just down.
So why doesn't the water flood in?
When you push the glass straight down, the air inside has nowhere to escape. It stays trapped, pressing outward against the water trying to enter.
The air pressure pushing out from inside equals the water pressure pushing in from outside. The two forces are balanced — and when forces are balanced, nothing moves. Water stays out. Air stays in. Your diver stays dry.
Think of it like two people pushing on opposite sides of a door with equal force. The door goes nowhere. The moment one stops — or you tilt the glass and a bubble escapes — the balance breaks and water floods in immediately.
Why does tilting ruin it?
Air is much lighter than water. Whenever a gap opens up, an air bubble escapes straight upward.
With the air gone, nothing is pushing back against the water anymore. The water floods in — and the air cave collapses.
Why does the tissue paper stay dry?
The tissue paper stays dry the entire time — not because you were quick, not because you were careful. Water physically cannot enter a space that is already occupied by air.
Two things cannot be in the same place at the same time. As long as the air is there first, the water has nowhere to go.
Curiosity spark
What do you think would happen if you pushed the glass deeper and deeper? Do you think the air bubble inside would get smaller, stay the same, or get bigger?
Find out in The Crazy Scientist Lab.
Try next
• See air pressure keeping liquid in place in a completely different way → [Drink Up]
• Watch air pressure create an invisible force that keeps a ball floating → [The Impossible Blow]
Extension: G&T Years 5 & 6
What is air pressure, really?
The air above us has mass — it weighs something. A column of air stretching from where you are standing all the way to the top of the atmosphere presses down on every square centimetre of the Earth's surface with enormous force. This is atmospheric pressure.
At sea level, atmospheric pressure is about 101,000 pascals — roughly the same as a 1-kilogram weight pressing on every square centimetre of your skin. You don't feel it because it pushes equally in all directions. Your body pushes back with the same force. Everything is in balance.
Push the glass underwater. Now water pressure adds to atmospheric pressure pushing against the trapped air. Does more water pressure mean more air is pushed into the glass — or that the air compresses? Make your prediction before reading on.
Why doesn't the water enter?
• The trapped air cannot escape while the glass is held straight. Water would only enter if it could push the air out of the way — but the air is pressing back with equal force. Neither wins. This balance is called pressure equilibrium.
• The moment you tilt the glass and a bubble escapes, the balance breaks. Water floods in immediately.
Vocabulary
Air pressure — the pushing force that air creates in all directions. The atmosphere above us pushes down on the Earth's surface, on water, and on anything in between.
Atmospheric pressure — air pressure caused by the weight of the entire atmosphere pressing down from above. At sea level this is the strongest air pressure we normally experience.
Trapped air — air enclosed in a space and unable to escape. In this experiment, the air inside the upside-down glass is trapped — it cannot escape past the water surrounding the rim.
Compress/compression — to squash something into a smaller space. When pressure on a trapped gas increases, the gas compresses — molecules are pushed closer together.
Know a parent or teacher who'd love this? Send it on! 👇
READY TO TEACH THIS
TOMORROW?
Running the experiment is easy; however, teaching it well is another challenge.
Teachers often ask:
How do I adapt this for Stages 1,2 or 3?
What do I do with fast finishers?
What misconceptions will they have?
How do I structure this for a full class?
What syllabus outcomes does it cover?
What do I say when they ask WHY?
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