PADI Divemaster Knowledge Review Exam: 200 Practice Questions
with Detailed Explanations – Based on the Latest 2025/2026 PADI
Standards
Section 1: Diving Physics (Questions 1–30)
Q1. A diver at 33 feet (10 meters) of seawater (33 fsw) experiences an ambient pressure of:
A) 1 atmosphere absolute (ATA)
B) 2 ATA
C) 3 ATA
D) 4 ATA
Answer: B) 2 ATA
Rationale: “: At sea level, pressure is 1 ATA. Every 33 feet (10 meters) of seawater adds another 1 ATA.
So at 33 feet, total pressure = 1 + 1 = 2 ATA.
Q2. If a flexible container holds 10 liters of air at the surface, what volume will it occupy at 66 feet (20
meters) of seawater?
A) 2.5 liters
B) 3.33 liters
C) 5 liters
D) 10 liters
Answer: B) 3.33 liters
Rationale: “: At 66 feet (20 m), pressure = 3 ATA (1 + 2). Boyle's Law: P1V1 = P2V2. (1 ATA × 10 L) = (3
ATA × V2) → V2 = 10/3 = 3.33 L.
Q3. A diver uses air at a rate of 20 liters per minute at the surface. What will be the approximate air
consumption rate at 66 feet (20 meters)?
A) 20 L/min
B) 40 L/min
C) 60 L/min
D) 80 L/min
Answer: C) 60 L/min
Rationale: “: Consumption increases proportionally with ambient pressure. At 66 feet (3 ATA),
consumption = 20 L/min × 3 = 60 L/min.
Q4. Which gas law explains why a diver should never hold their breath while ascending?
A) Henry's Law
B) Charles' Law
C) Boyle's Law
D) Dalton's Law
,Answer: C) Boyle's Law
Rationale: “: Boyle's Law describes the inverse relationship between pressure and volume. As a diver
ascends, pressure decreases, so lung volume would expand dangerously if breath is held.
Q5. According to Charles' Law, if a scuba cylinder is filled with air at 70°F and then heated to 100°F, the
pressure inside will:
A) Decrease
B) Stay the same
C) Increase
D) Drop to zero
Answer: C) Increase
Rationale: “: Charles' Law states that at constant volume, pressure is directly proportional to absolute
temperature. Heating increases pressure.
Q6. The partial pressure of oxygen (PO2) in air at sea level is approximately:
A) 0.21 ATA
B) 0.79 ATA
C) 1.0 ATA
D) 0.16 ATA
Answer: A) 0.21 ATA
Rationale: “: At sea level, total pressure = 1 ATA. Air is 21% oxygen, so PO2 = 0.21 × 1 ATA = 0.21 ATA
(Dalton's Law).
Q7. A diver breathing air (21% O2) at 99 feet (30 meters) will have a PO2 of:
A) 0.21 ATA
B) 0.63 ATA
C) 0.84 ATA
D) 1.0 ATA
Answer: C) 0.84 ATA
Rationale: “: At 99 feet, pressure = 4 ATA (1 + 3). PO2 = 0.21 × 4 ATA = 0.84 ATA.
Q8. The maximum recommended PO2 for recreational diving is:
A) 0.5 ATA
B) 1.0 ATA
C) 1.4 ATA
D) 2.0 ATA
Answer: C) 1.4 ATA
Rationale: “: PADI standards recommend a maximum PO2 of 1.4 ATA for the working portion of a dive
and 1.6 ATA for the decompression (or contingency) segment.
Q9. The condition caused by nitrogen dissolving into body tissues under pressure and forming bubbles
during ascent is called:
A) Oxygen toxicity
B) Decompression sickness (DCS)
,C) Nitrogen narcosis
D) Arterial gas embolism
Answer: B) Decompression sickness (DCS)
Rationale: “: DCS results from inert gas (usually nitrogen) coming out of solution and forming bubbles in
tissues and blood when ambient pressure decreases too rapidly.
Q10. A diver feels joint pain and skin rash after a rapid ascent. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Carbon monoxide poisoning
D) Hypothermia
Answer: A) Decompression sickness
Rationale: “: Joint pain (the "bends") and skin rash are common symptoms of DCS, typically
occurring within minutes to hours after a dive.
Q11. The primary reason for using dive tables or a dive computer is to:
A) Avoid running out of air
B) Prevent decompression sickness
C) Measure depth accurately
D) Improve buoyancy control
Answer: B) Prevent decompression sickness
Rationale: “: Decompression tools help divers track nitrogen absorption and ensure they stay within
no-decompression limits or follow appropriate ascent schedules.
Q12. A diver experiences confusion, euphoria, and overconfidence at 130 feet. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Oxygen toxicity
D) Hypothermia
Answer: B) Nitrogen narcosis
Rationale: “: Nitrogen narcosis ("rapture of the deep") is caused by the increased partial pressure of
nitrogen at depth, producing symptoms similar to alcohol intoxication.
Q13. The limiting factor for a no-decompression dive is:
A) Air supply only
B) Nitrogen absorption
C) Water temperature
D) Visibility
Answer: B) Nitrogen absorption
Rationale: “: A no-decompression dive allows a diver to ascend directly to the surface without staged
stops because the absorbed nitrogen remains within acceptable limits. The dive time is limited by how
much nitrogen the body can tolerate.
, Q14. A diver ascends from 60 feet in 30 seconds, holds their breath, and immediately loses
consciousness. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Arterial gas embolism (AGE)
D) Hypoxia
Answer: C) Arterial gas embolism (AGE)
Rationale: “: Holding breath during ascent causes lung overexpansion, forcing air into the arterial
system, which can lead to stroke-like symptoms or unconsciousness, often immediately upon surfacing.
Q15. The first aid for a suspected arterial gas embolism includes:
A) Recompression in a hyperbaric chamber as soon as possible
B) Administering 100% oxygen
C) Placing the diver in a supine position
D) Both A and B
Answer: D) Both A and B
Rationale: “: High-flow oxygen is critical first aid, and urgent evacuation to a recompression chamber is
essential for both AGE and DCS.
Q16. The refractive index difference between air and water causes underwater objects to appear:
A) Larger and closer
B) Smaller and farther
C) The same size but discolored
D) Larger but farther
Answer: A) Larger and closer
Rationale: “: Light bends when entering the mask, magnifying objects by about 33% and making them
appear closer by approximately 25%.
Q17. Sound travels underwater:
A) Slower than in air
B) At the same speed as in air
C) Faster than in air
D) Not at all
Answer: C) Faster than in air
Rationale: “: Sound travels about 4-5 times faster in water due to higher density, making directionality
very difficult underwater.
Q18. The greatest heat loss from a diver's body occurs through:
A) Respiration
B) Head (if uncovered)
C) Conduction to water
D) Evaporation
with Detailed Explanations – Based on the Latest 2025/2026 PADI
Standards
Section 1: Diving Physics (Questions 1–30)
Q1. A diver at 33 feet (10 meters) of seawater (33 fsw) experiences an ambient pressure of:
A) 1 atmosphere absolute (ATA)
B) 2 ATA
C) 3 ATA
D) 4 ATA
Answer: B) 2 ATA
Rationale: “: At sea level, pressure is 1 ATA. Every 33 feet (10 meters) of seawater adds another 1 ATA.
So at 33 feet, total pressure = 1 + 1 = 2 ATA.
Q2. If a flexible container holds 10 liters of air at the surface, what volume will it occupy at 66 feet (20
meters) of seawater?
A) 2.5 liters
B) 3.33 liters
C) 5 liters
D) 10 liters
Answer: B) 3.33 liters
Rationale: “: At 66 feet (20 m), pressure = 3 ATA (1 + 2). Boyle's Law: P1V1 = P2V2. (1 ATA × 10 L) = (3
ATA × V2) → V2 = 10/3 = 3.33 L.
Q3. A diver uses air at a rate of 20 liters per minute at the surface. What will be the approximate air
consumption rate at 66 feet (20 meters)?
A) 20 L/min
B) 40 L/min
C) 60 L/min
D) 80 L/min
Answer: C) 60 L/min
Rationale: “: Consumption increases proportionally with ambient pressure. At 66 feet (3 ATA),
consumption = 20 L/min × 3 = 60 L/min.
Q4. Which gas law explains why a diver should never hold their breath while ascending?
A) Henry's Law
B) Charles' Law
C) Boyle's Law
D) Dalton's Law
,Answer: C) Boyle's Law
Rationale: “: Boyle's Law describes the inverse relationship between pressure and volume. As a diver
ascends, pressure decreases, so lung volume would expand dangerously if breath is held.
Q5. According to Charles' Law, if a scuba cylinder is filled with air at 70°F and then heated to 100°F, the
pressure inside will:
A) Decrease
B) Stay the same
C) Increase
D) Drop to zero
Answer: C) Increase
Rationale: “: Charles' Law states that at constant volume, pressure is directly proportional to absolute
temperature. Heating increases pressure.
Q6. The partial pressure of oxygen (PO2) in air at sea level is approximately:
A) 0.21 ATA
B) 0.79 ATA
C) 1.0 ATA
D) 0.16 ATA
Answer: A) 0.21 ATA
Rationale: “: At sea level, total pressure = 1 ATA. Air is 21% oxygen, so PO2 = 0.21 × 1 ATA = 0.21 ATA
(Dalton's Law).
Q7. A diver breathing air (21% O2) at 99 feet (30 meters) will have a PO2 of:
A) 0.21 ATA
B) 0.63 ATA
C) 0.84 ATA
D) 1.0 ATA
Answer: C) 0.84 ATA
Rationale: “: At 99 feet, pressure = 4 ATA (1 + 3). PO2 = 0.21 × 4 ATA = 0.84 ATA.
Q8. The maximum recommended PO2 for recreational diving is:
A) 0.5 ATA
B) 1.0 ATA
C) 1.4 ATA
D) 2.0 ATA
Answer: C) 1.4 ATA
Rationale: “: PADI standards recommend a maximum PO2 of 1.4 ATA for the working portion of a dive
and 1.6 ATA for the decompression (or contingency) segment.
Q9. The condition caused by nitrogen dissolving into body tissues under pressure and forming bubbles
during ascent is called:
A) Oxygen toxicity
B) Decompression sickness (DCS)
,C) Nitrogen narcosis
D) Arterial gas embolism
Answer: B) Decompression sickness (DCS)
Rationale: “: DCS results from inert gas (usually nitrogen) coming out of solution and forming bubbles in
tissues and blood when ambient pressure decreases too rapidly.
Q10. A diver feels joint pain and skin rash after a rapid ascent. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Carbon monoxide poisoning
D) Hypothermia
Answer: A) Decompression sickness
Rationale: “: Joint pain (the "bends") and skin rash are common symptoms of DCS, typically
occurring within minutes to hours after a dive.
Q11. The primary reason for using dive tables or a dive computer is to:
A) Avoid running out of air
B) Prevent decompression sickness
C) Measure depth accurately
D) Improve buoyancy control
Answer: B) Prevent decompression sickness
Rationale: “: Decompression tools help divers track nitrogen absorption and ensure they stay within
no-decompression limits or follow appropriate ascent schedules.
Q12. A diver experiences confusion, euphoria, and overconfidence at 130 feet. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Oxygen toxicity
D) Hypothermia
Answer: B) Nitrogen narcosis
Rationale: “: Nitrogen narcosis ("rapture of the deep") is caused by the increased partial pressure of
nitrogen at depth, producing symptoms similar to alcohol intoxication.
Q13. The limiting factor for a no-decompression dive is:
A) Air supply only
B) Nitrogen absorption
C) Water temperature
D) Visibility
Answer: B) Nitrogen absorption
Rationale: “: A no-decompression dive allows a diver to ascend directly to the surface without staged
stops because the absorbed nitrogen remains within acceptable limits. The dive time is limited by how
much nitrogen the body can tolerate.
, Q14. A diver ascends from 60 feet in 30 seconds, holds their breath, and immediately loses
consciousness. This is most likely:
A) Decompression sickness
B) Nitrogen narcosis
C) Arterial gas embolism (AGE)
D) Hypoxia
Answer: C) Arterial gas embolism (AGE)
Rationale: “: Holding breath during ascent causes lung overexpansion, forcing air into the arterial
system, which can lead to stroke-like symptoms or unconsciousness, often immediately upon surfacing.
Q15. The first aid for a suspected arterial gas embolism includes:
A) Recompression in a hyperbaric chamber as soon as possible
B) Administering 100% oxygen
C) Placing the diver in a supine position
D) Both A and B
Answer: D) Both A and B
Rationale: “: High-flow oxygen is critical first aid, and urgent evacuation to a recompression chamber is
essential for both AGE and DCS.
Q16. The refractive index difference between air and water causes underwater objects to appear:
A) Larger and closer
B) Smaller and farther
C) The same size but discolored
D) Larger but farther
Answer: A) Larger and closer
Rationale: “: Light bends when entering the mask, magnifying objects by about 33% and making them
appear closer by approximately 25%.
Q17. Sound travels underwater:
A) Slower than in air
B) At the same speed as in air
C) Faster than in air
D) Not at all
Answer: C) Faster than in air
Rationale: “: Sound travels about 4-5 times faster in water due to higher density, making directionality
very difficult underwater.
Q18. The greatest heat loss from a diver's body occurs through:
A) Respiration
B) Head (if uncovered)
C) Conduction to water
D) Evaporation
