PADI OPEN WATER FINAL EXAM B
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2026 Q&A |LATEST EXAM UPDATE
2026/2027.
Question 1
A diver descends from the surface to 10 meters (33 feet). The ambient pressure
increases from 1 atmosphere to 2 atmospheres absolute (ATA). What happens to
the volume of a flexible air-filled space (e.g., a diver's lungs, a balloon)?
A) It doubles
B) It is reduced to one-half
C) It remains the same
D) It increases by 50%
Correct Answer: B
Rationale: Boyle's Law states that at constant temperature, the volume of a gas is
inversely proportional to absolute pressure. At 10 meters, pressure is 2 ATA (1 atm
from water + 1 atm from atmosphere). Volume = 1/2 of surface volume.
Question 2
If a diver descends to 20 meters (66 feet), the ambient pressure is:
,A) 2 ATA
B) 3 ATA
C) 4 ATA
D) 1 ATA
Correct Answer: B
Rationale: For every 10 meters (33 feet) of seawater, pressure increases by 1 ATA.
At 20 meters, water pressure = 2 ATA; plus surface atmospheric pressure of 1 ATA
= 3 ATA total.
Question 3
The absolute pressure at 40 meters (132 feet) of seawater is:
A) 4 ATA
B) 5 ATA
C) 6 ATA
D) 3 ATA
Correct Answer: B
Rationale: 40 meters water pressure = 4 ATA (40 m ÷ 10 m per ATA); plus surface 1
ATA = 5 ATA total.
Question 4
A diver inflates a lift bag at 20 meters (3 ATA) with 10 liters of air. If the bag ascends
to the surface, what will its volume be (assuming no air loss and constant
temperature)?
,A) 10 liters
B) 20 liters
C) 30 liters
D) 40 liters
Correct Answer: C
Rationale: P₁V₁ = P₂V₂. (3 ATA)(10 L) = (1 ATA)(V₂). V₂ = 30 L. The bag will expand
threefold, illustrating why a lift bag must be vented during ascent.
Question 5
As you descend in water, the surrounding pressure:
A) Decreases
B) Stays the same
C) Increases
D) Fluctuates randomly
Correct Answer: C
Rationale: Water pressure increases with depth due to the weight of the water
above. Every 10 meters (33 feet) of seawater adds approximately 1 bar (ATA) of
pressure.
Question 6
A depth change of 10 meters (33 feet) causes a pressure change of:
, A) 0.5 bar/ATA
B) 1 bar/ATA
C) 2 bar/ATA
D) 3 bar/ATA
Correct Answer: B
Rationale: For every 10 meters (33 feet) of depth change, pressure changes by
exactly 1 bar/ATA. This is a fundamental rule derived from the weight of a column of
water.
Question 7
I turn a glass upside down, trap the air in it by putting it in water, and then I take the
glass down to 10 meters. The air space would:
A) Become half the size it was at the surface
B) Not change in size
C) Become 1/3 the size it was at the surface
D) Become 2/3 the size it was at the surface
Correct Answer: A
Rationale: At 10 meters, the pressure is 2 bar. An air volume taken to this depth
from the surface would decrease and become half the size.
Question 8
If my cylinder of air lasts 60 minutes while I am at the surface breathing normally,
assuming all else is the same, how long will it last at 20 meters breathing normally?
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2026 Q&A |LATEST EXAM UPDATE
2026/2027.
Question 1
A diver descends from the surface to 10 meters (33 feet). The ambient pressure
increases from 1 atmosphere to 2 atmospheres absolute (ATA). What happens to
the volume of a flexible air-filled space (e.g., a diver's lungs, a balloon)?
A) It doubles
B) It is reduced to one-half
C) It remains the same
D) It increases by 50%
Correct Answer: B
Rationale: Boyle's Law states that at constant temperature, the volume of a gas is
inversely proportional to absolute pressure. At 10 meters, pressure is 2 ATA (1 atm
from water + 1 atm from atmosphere). Volume = 1/2 of surface volume.
Question 2
If a diver descends to 20 meters (66 feet), the ambient pressure is:
,A) 2 ATA
B) 3 ATA
C) 4 ATA
D) 1 ATA
Correct Answer: B
Rationale: For every 10 meters (33 feet) of seawater, pressure increases by 1 ATA.
At 20 meters, water pressure = 2 ATA; plus surface atmospheric pressure of 1 ATA
= 3 ATA total.
Question 3
The absolute pressure at 40 meters (132 feet) of seawater is:
A) 4 ATA
B) 5 ATA
C) 6 ATA
D) 3 ATA
Correct Answer: B
Rationale: 40 meters water pressure = 4 ATA (40 m ÷ 10 m per ATA); plus surface 1
ATA = 5 ATA total.
Question 4
A diver inflates a lift bag at 20 meters (3 ATA) with 10 liters of air. If the bag ascends
to the surface, what will its volume be (assuming no air loss and constant
temperature)?
,A) 10 liters
B) 20 liters
C) 30 liters
D) 40 liters
Correct Answer: C
Rationale: P₁V₁ = P₂V₂. (3 ATA)(10 L) = (1 ATA)(V₂). V₂ = 30 L. The bag will expand
threefold, illustrating why a lift bag must be vented during ascent.
Question 5
As you descend in water, the surrounding pressure:
A) Decreases
B) Stays the same
C) Increases
D) Fluctuates randomly
Correct Answer: C
Rationale: Water pressure increases with depth due to the weight of the water
above. Every 10 meters (33 feet) of seawater adds approximately 1 bar (ATA) of
pressure.
Question 6
A depth change of 10 meters (33 feet) causes a pressure change of:
, A) 0.5 bar/ATA
B) 1 bar/ATA
C) 2 bar/ATA
D) 3 bar/ATA
Correct Answer: B
Rationale: For every 10 meters (33 feet) of depth change, pressure changes by
exactly 1 bar/ATA. This is a fundamental rule derived from the weight of a column of
water.
Question 7
I turn a glass upside down, trap the air in it by putting it in water, and then I take the
glass down to 10 meters. The air space would:
A) Become half the size it was at the surface
B) Not change in size
C) Become 1/3 the size it was at the surface
D) Become 2/3 the size it was at the surface
Correct Answer: A
Rationale: At 10 meters, the pressure is 2 bar. An air volume taken to this depth
from the surface would decrease and become half the size.
Question 8
If my cylinder of air lasts 60 minutes while I am at the surface breathing normally,
assuming all else is the same, how long will it last at 20 meters breathing normally?
