At one spot in the same calm water, vertical depth sets the reading. Pressure pushes from every side; adding water only sideways keeps that spot unchanged.
vertical: depthall around: pressure
The balloon is a model for trapped gas—not a claim that a person shrinks. Open each careful limit.
Do people shrink like balloons?+
No. A balloon exaggerates what pressure does to trapped gas. Most of your body is water-rich and does not visibly shrink; air spaces such as the middle ear and lungs are different.
Does every liquid add pressure alike?+
Not at the same rate. At equal vertical depth and gravity, a denser liquid adds more pressure than a less-dense one.
What if your ears hurt underwater?+
Stop going down. Return toward the surface in control and tell a grown-up. Never force yourself deeper or copy a deep-water or pressure-chamber test.
SAME 4-MARK DEPTH
EQUAL PRESSURE · EQUAL AIR SIZE
DEPTH: 4 vs 7 MARKS
7 → MORE PRESSURE → LESS AIR SPACE
Count the vertical water depth above the spot—not the whole pool. In the same calm water, greater depth means more pressure, fitting the same sealed air into less space.
psst, grown-ups →
For a static fluid, gauge pressure is ΔP = ρgh: density, gravity, and vertical depth set the added pressure, not container width or total volume. Pressure at a point is isotropic. A flexible sealed gas pocket responds approximately through Boyle’s law, P₁V₁ ≈ P₂V₂ at constant temperature. The balloon is not a model of a whole person: water-rich tissue changes volume very little, while pressure differences across gas spaces such as the middle ear matter. This story is a simulation, not a diving experiment.