PADI Open Water Diver | Professional Association
of Diving Instructors | Academic Year 2026/2027
SECTION 1: DIVE PHYSICS & PHYSIOLOGY
Q1. According to Boyle's Law, what happens to the volume of air in a flexible
container as a diver descends from the surface to 33 feet (10 meters) of
seawater?
A) The volume doubles
B) The volume remains unchanged
C) The volume is reduced to one-half
D) The volume is reduced to one-third
Correct Answer: C) The volume is reduced to one-half
Rationale: Boyle's Law states that pressure and volume are inversely
proportional. At 33 feet of seawater, ambient pressure is 2 atmospheres absolute
(ATA). Therefore, air volume is compressed to one-half of its original volume. This
principle explains why divers must equalize air spaces and never hold their breath
during ascent.
Q2. A diver at 10 meters (33 feet) in salt water experiences an absolute pressure
of:
A) 1 bar/ata
B) 2 bar/ata
C) 3 bar/ata
D) 4 bar/ata
Correct Answer: B) 2 bar/ata
Rationale: At the surface, pressure is 1 bar/ata. Seawater pressure
increases by 1 bar/ata for every 10 meters/33 feet of depth. Therefore, at 10
,meters/33 feet, the absolute pressure is 2 bar/ata (1 surface + 1 from water
depth).
Q3. A depth change of 10 meters/33 feet causes a pressure change of:
A) 1 bar/ata
B) 2 bar/ata
C) 0.5 bar/ata
D) 3 bar/ata
Correct Answer: A) 1 bar/ata
Rationale: Water pressure increases by approximately 1 bar/ata for every
10 meters/33 feet of depth change. This is a fundamental principle used in dive
planning and understanding how pressure affects air spaces in the body and
equipment.
Q4. A diver takes 6 liters of air from the surface to 20 meters/66 feet. What will
the volume be at depth?
A) 6 liters
B) 3 liters
C) 2 liters
D) 1 liter
Correct Answer: C) 2 liters
Rationale: At 20 meters/66 feet, absolute pressure is 3 bar/ata (1 at
surface + 2 from depth). According to Boyle's Law (P₁V₁ = P₂V₂), 6 liters × 1 bar = V₂
× 3 bar, so V₂ = 2 liters. The density of the air would be three times the density at
the surface.
Q5. As you descend in water, the pressure:
A) Decreases
B) Remains the same
,C) Increases
D) Fluctuates randomly
Correct Answer: C) Increases
Rationale: As depth increases, the weight of the water above increases,
causing pressure to increase. This is why divers must equalize their ears and
sinuses during descent and why air consumption increases with depth due to gas
density.
Q6. A balloon fully inflated and sealed at 10 meters/33 feet would probably
______ during ascent to the surface.
A) Shrink
B) Remain the same size
C) Burst
D) Fill with water
Correct Answer: C) Burst
Rationale: As the balloon ascends, ambient pressure decreases, causing
the air inside to expand. The volume doubles from 2 ATA to 1 ATA. A balloon
sealed at depth may burst during ascent because the expanding air has nowhere
to escape. This illustrates why divers must never hold their breath.
Q7. A squeeze is caused by:
A) Nitrogen absorption
B) A pressure imbalance between the surrounding pressure and an air space
C) Excess oxygen in the tissues
D) Rapid ascent
Correct Answer: B) A pressure imbalance between the surrounding
pressure and an air space
Rationale: A squeeze occurs when the pressure inside an air space (mask,
ears, sinuses, lungs, etc.) is less than the surrounding water pressure. The air
, space compresses, causing tissue damage or discomfort. Equalization prevents
squeezes.
Q8. As I descend, increasing pressure affects my:
A) Mask, ears, and sinuses
B) Skin only
C) Muscles only
D) Fins only
Correct Answer: A) Mask, ears, and sinuses
Rationale: Increasing pressure affects all air spaces in the body, including
the mask (which traps air), ears, and sinuses. These air spaces must be equalized
during descent to prevent discomfort, squeeze, or injury.
Q9. The most important rule in scuba diving is:
A) Always dive with a buddy
B) Breathe continuously and never hold your breath
C) Check your air supply frequently
D) Ascend slowly
Correct Answer: B) Breathe continuously and never hold your breath
Rationale: Breathing continuously is the most critical rule because
expanding air during ascent must be allowed to escape. Holding your breath while
ascending can cause lung overexpansion injury (pulmonary barotrauma), which
can be fatal.
Q10. During ascent, I feel discomfort in my ears. I should:
A) Continue ascending rapidly
B) Stop, descend slightly, and allow trapped air to work its way out
C) Hold my breath and force the air out
D) Ignore the discomfort
of Diving Instructors | Academic Year 2026/2027
SECTION 1: DIVE PHYSICS & PHYSIOLOGY
Q1. According to Boyle's Law, what happens to the volume of air in a flexible
container as a diver descends from the surface to 33 feet (10 meters) of
seawater?
A) The volume doubles
B) The volume remains unchanged
C) The volume is reduced to one-half
D) The volume is reduced to one-third
Correct Answer: C) The volume is reduced to one-half
Rationale: Boyle's Law states that pressure and volume are inversely
proportional. At 33 feet of seawater, ambient pressure is 2 atmospheres absolute
(ATA). Therefore, air volume is compressed to one-half of its original volume. This
principle explains why divers must equalize air spaces and never hold their breath
during ascent.
Q2. A diver at 10 meters (33 feet) in salt water experiences an absolute pressure
of:
A) 1 bar/ata
B) 2 bar/ata
C) 3 bar/ata
D) 4 bar/ata
Correct Answer: B) 2 bar/ata
Rationale: At the surface, pressure is 1 bar/ata. Seawater pressure
increases by 1 bar/ata for every 10 meters/33 feet of depth. Therefore, at 10
,meters/33 feet, the absolute pressure is 2 bar/ata (1 surface + 1 from water
depth).
Q3. A depth change of 10 meters/33 feet causes a pressure change of:
A) 1 bar/ata
B) 2 bar/ata
C) 0.5 bar/ata
D) 3 bar/ata
Correct Answer: A) 1 bar/ata
Rationale: Water pressure increases by approximately 1 bar/ata for every
10 meters/33 feet of depth change. This is a fundamental principle used in dive
planning and understanding how pressure affects air spaces in the body and
equipment.
Q4. A diver takes 6 liters of air from the surface to 20 meters/66 feet. What will
the volume be at depth?
A) 6 liters
B) 3 liters
C) 2 liters
D) 1 liter
Correct Answer: C) 2 liters
Rationale: At 20 meters/66 feet, absolute pressure is 3 bar/ata (1 at
surface + 2 from depth). According to Boyle's Law (P₁V₁ = P₂V₂), 6 liters × 1 bar = V₂
× 3 bar, so V₂ = 2 liters. The density of the air would be three times the density at
the surface.
Q5. As you descend in water, the pressure:
A) Decreases
B) Remains the same
,C) Increases
D) Fluctuates randomly
Correct Answer: C) Increases
Rationale: As depth increases, the weight of the water above increases,
causing pressure to increase. This is why divers must equalize their ears and
sinuses during descent and why air consumption increases with depth due to gas
density.
Q6. A balloon fully inflated and sealed at 10 meters/33 feet would probably
______ during ascent to the surface.
A) Shrink
B) Remain the same size
C) Burst
D) Fill with water
Correct Answer: C) Burst
Rationale: As the balloon ascends, ambient pressure decreases, causing
the air inside to expand. The volume doubles from 2 ATA to 1 ATA. A balloon
sealed at depth may burst during ascent because the expanding air has nowhere
to escape. This illustrates why divers must never hold their breath.
Q7. A squeeze is caused by:
A) Nitrogen absorption
B) A pressure imbalance between the surrounding pressure and an air space
C) Excess oxygen in the tissues
D) Rapid ascent
Correct Answer: B) A pressure imbalance between the surrounding
pressure and an air space
Rationale: A squeeze occurs when the pressure inside an air space (mask,
ears, sinuses, lungs, etc.) is less than the surrounding water pressure. The air
, space compresses, causing tissue damage or discomfort. Equalization prevents
squeezes.
Q8. As I descend, increasing pressure affects my:
A) Mask, ears, and sinuses
B) Skin only
C) Muscles only
D) Fins only
Correct Answer: A) Mask, ears, and sinuses
Rationale: Increasing pressure affects all air spaces in the body, including
the mask (which traps air), ears, and sinuses. These air spaces must be equalized
during descent to prevent discomfort, squeeze, or injury.
Q9. The most important rule in scuba diving is:
A) Always dive with a buddy
B) Breathe continuously and never hold your breath
C) Check your air supply frequently
D) Ascend slowly
Correct Answer: B) Breathe continuously and never hold your breath
Rationale: Breathing continuously is the most critical rule because
expanding air during ascent must be allowed to escape. Holding your breath while
ascending can cause lung overexpansion injury (pulmonary barotrauma), which
can be fatal.
Q10. During ascent, I feel discomfort in my ears. I should:
A) Continue ascending rapidly
B) Stop, descend slightly, and allow trapped air to work its way out
C) Hold my breath and force the air out
D) Ignore the discomfort
