PADI OPEN WATER EXAM 200 ACTUAL QUESTIONS AND
CORRECT ANSWERS WITH RATIONALE LATEST 2026
ASSURED PASS!!!!!!!!!!!!!!!!!
This comprehensive 200-question bank is designed for the PADI Open Water
Diver exam, covering the full scope of entry-level scuba diving knowledge.
Each question presents a unique, technically focused scenario testing physics
(Boyle's, Dalton's, Henry's laws), physiology (equalization, nitrogen narcosis,
decompression sickness, lung overexpansion), equipment (BCD, regulator,
cylinder, valves, mask, fins, snorkel), dive planning (RDP tables, safety stops,
ascent rates, repetitive diving), emergency procedures (out-of-air drills,
CESA, buddy separation), and environmental awareness (currents, marine
life, visibility). Each question includes a detailed rationale to reinforce
understanding. No questions are repeated, ensuring broad content coverage
for effective exam preparation and certification success.
1. According to Boyle's law, if a diver descends from the surface to 20 meters (66
feet) of sea water, the volume of a flexible air-filled space will:
A. Increase to three times its original volume
B. Decrease to one-third of its original volume
C. Decrease to one-half of its original volume
D. Remain the same
Answer: B. Decrease to one-third
Rationale: Pressure at 20 meters is 3 ATA (1 atm surface + 2 atm water). Volume
is inversely proportional to pressure, so volume becomes 1/3 of surface volume.
2. The absolute pressure at 30 meters (99 feet) of sea water is approximately:
A. 2 ATA
B. 3 ATA
C. 4 ATA
D. 5 ATA
Answer: C. 4 ATA
Rationale: Each 10 meters of seawater adds 1 ATA of pressure. At 30 meters,
water pressure is 3 ATA, plus surface atmospheric pressure of 1 ATA, for a total of
4 ATA absolute.
,3. If a diver's air consumption rate at the surface is 25 liters per minute, at 40
meters (5 ATA) the consumption rate will be approximately:
A. 25 L/min
B. 50 L/min
C. 100 L/min
D. 125 L/min
Answer: D. 125 L/min
Rationale: Air consumption is proportional to ambient pressure. At 40 meters,
pressure is 5 ATA, so consumption = 25 L/min × 5 = 125 L/min.
4. A diver holding their breath while ascending from 30 meters to the surface risks:
A. Nitrogen narcosis
B. Oxygen toxicity
C. Lung overexpansion injury (arterial gas embolism)
D. Decompression sickness
Answer: C. Lung overexpansion injury (arterial gas embolism)
Rationale: As a diver ascends, the air in the lungs expands. Holding the breath
prevents this expanding air from escaping, which can rupture lung tissue and force
gas bubbles into the arterial circulation, causing an arterial gas embolism.
5. The most important rule in scuba diving is to:
A. Check your air every 5 minutes
B. Dive with a buddy
C. Breathe continuously and never hold your breath
D. Plan your dive and dive your plan
Answer: C. Breathe continuously and never hold your breath
Rationale: This is the primary rule to prevent lung overexpansion injury. Holding
your breath during ascent is life-threatening and can result in paralysis or death.
6. If an object is neutrally buoyant in fresh water, it will ______ in salt water:
A. Sink
B. Float
C. Remain neutrally buoyant
D. Sink then float
Answer: B. Float
Rationale: Salt water is denser than fresh water because of dissolved minerals. This
means it causes more upward force (buoyancy). An object that is neutrally buoyant
in fresh water would float in salt water.
,7. I blow up a balloon, tie it off, and take it to the bottom of the swimming pool.
What will happen to the balloon and the air inside it?
A. The balloon will get bigger and the air inside will be less dense
B. The balloon will get smaller and the air inside will be more dense
C. The balloon will get bigger and the air inside will be more dense
D. The balloon will get smaller and the air inside will be less dense
Answer: B. The balloon will get smaller and the air inside will be more dense
Rationale: As water pressure increases, the volume of an air space decreases. This
causes the density of the air inside to increase as molecules are pushed closer
together.
8. If I am not able to equalize (clear) my body air spaces, it may be because I have:
A. Seasickness
B. Heart disease and high blood pressure
C. A cold, allergy, or another medical problem
D. Anxiety
Answer: C. A cold, allergy, or another medical problem
Rationale: A cold or congestion can block air passages in the ears and sinuses,
making equalization difficult or impossible. Divers should cancel a dive if they are
congested.
9. If my ears or sinuses hurt while I am descending (going down), it usually means:
A. My air spaces are equalized
B. My mask strap is too tight
C. I am feeling a squeeze and need to equalize
D. My mask is too small
Answer: C. I am feeling a squeeze and need to equalize
Rationale: Pain in the ears or sinuses during descent means they aren't equalized.
The diver should stop the descent, ascend slightly to relieve pressure, and attempt
to equalize again. If unable, the dive should be ended.
10. Lung overexpansion injuries can be caused by:
A. Scuba diving without a buddy
B. Continuing a dive when not properly weighted
C. Not drinking enough water before scuba diving
D. Holding my breath while scuba diving
Answer: D. Holding my breath while scuba diving
Rationale: Blocking off the lungs by holding the breath and ascending could cause
them to overexpand and rupture, which is a serious injury that could result in
paralysis and death.
, 11. If my cylinder of air lasts 60 minutes while I am at the surface breathing
normally, how long will it last at 20 meters (66 feet) breathing normally?
A. 60 minutes
B. 20 minutes
C. 15 minutes
D. 12 minutes
Answer: B. 20 minutes
Rationale: At 20 meters, pressure is 3 ATA (1 atm surface + 2 atm water). Air
consumption increases proportionally, so the tank will last 60/3 = 20 minutes.
12. The best place for me to position an alternate air source is:
A. Loose by my side so I can find it fast
B. In the triangle area formed by my chin and the lower corners of my rib cage
C. To the base of my cylinder
D. To the back of my BCD between my shoulder blades and waist
Answer: B. In the triangle area formed by my chin and the lower corners of my rib
cage
Rationale: The alternate air source should be secured with a quick-release in the
triangle area formed by the chin and the lower corners of the rib cage. It should
never dangle unsecured from the kit.
13. How often should I take my scuba cylinder to be visually inspected by my dive
center?
A. Once a year
B. Once every two years
C. Every six months
D. Every five years
Answer: A. Once a year
Rationale: Scuba cylinders require an annual visual inspection for internal
corrosion or other contamination or damage. A hydrostatic test is required every
five years.
14. The difference between DIN valves and yoke valves is that DIN valves:
A. Are made from durable plastic
B. Contain a spring-operated shutoff valve held open by cylinder pressure
C. Have an o-ring in them
D. Have threaded openings to screw the regulator into
Answer: D. Have threaded openings to screw the regulator into
CORRECT ANSWERS WITH RATIONALE LATEST 2026
ASSURED PASS!!!!!!!!!!!!!!!!!
This comprehensive 200-question bank is designed for the PADI Open Water
Diver exam, covering the full scope of entry-level scuba diving knowledge.
Each question presents a unique, technically focused scenario testing physics
(Boyle's, Dalton's, Henry's laws), physiology (equalization, nitrogen narcosis,
decompression sickness, lung overexpansion), equipment (BCD, regulator,
cylinder, valves, mask, fins, snorkel), dive planning (RDP tables, safety stops,
ascent rates, repetitive diving), emergency procedures (out-of-air drills,
CESA, buddy separation), and environmental awareness (currents, marine
life, visibility). Each question includes a detailed rationale to reinforce
understanding. No questions are repeated, ensuring broad content coverage
for effective exam preparation and certification success.
1. According to Boyle's law, if a diver descends from the surface to 20 meters (66
feet) of sea water, the volume of a flexible air-filled space will:
A. Increase to three times its original volume
B. Decrease to one-third of its original volume
C. Decrease to one-half of its original volume
D. Remain the same
Answer: B. Decrease to one-third
Rationale: Pressure at 20 meters is 3 ATA (1 atm surface + 2 atm water). Volume
is inversely proportional to pressure, so volume becomes 1/3 of surface volume.
2. The absolute pressure at 30 meters (99 feet) of sea water is approximately:
A. 2 ATA
B. 3 ATA
C. 4 ATA
D. 5 ATA
Answer: C. 4 ATA
Rationale: Each 10 meters of seawater adds 1 ATA of pressure. At 30 meters,
water pressure is 3 ATA, plus surface atmospheric pressure of 1 ATA, for a total of
4 ATA absolute.
,3. If a diver's air consumption rate at the surface is 25 liters per minute, at 40
meters (5 ATA) the consumption rate will be approximately:
A. 25 L/min
B. 50 L/min
C. 100 L/min
D. 125 L/min
Answer: D. 125 L/min
Rationale: Air consumption is proportional to ambient pressure. At 40 meters,
pressure is 5 ATA, so consumption = 25 L/min × 5 = 125 L/min.
4. A diver holding their breath while ascending from 30 meters to the surface risks:
A. Nitrogen narcosis
B. Oxygen toxicity
C. Lung overexpansion injury (arterial gas embolism)
D. Decompression sickness
Answer: C. Lung overexpansion injury (arterial gas embolism)
Rationale: As a diver ascends, the air in the lungs expands. Holding the breath
prevents this expanding air from escaping, which can rupture lung tissue and force
gas bubbles into the arterial circulation, causing an arterial gas embolism.
5. The most important rule in scuba diving is to:
A. Check your air every 5 minutes
B. Dive with a buddy
C. Breathe continuously and never hold your breath
D. Plan your dive and dive your plan
Answer: C. Breathe continuously and never hold your breath
Rationale: This is the primary rule to prevent lung overexpansion injury. Holding
your breath during ascent is life-threatening and can result in paralysis or death.
6. If an object is neutrally buoyant in fresh water, it will ______ in salt water:
A. Sink
B. Float
C. Remain neutrally buoyant
D. Sink then float
Answer: B. Float
Rationale: Salt water is denser than fresh water because of dissolved minerals. This
means it causes more upward force (buoyancy). An object that is neutrally buoyant
in fresh water would float in salt water.
,7. I blow up a balloon, tie it off, and take it to the bottom of the swimming pool.
What will happen to the balloon and the air inside it?
A. The balloon will get bigger and the air inside will be less dense
B. The balloon will get smaller and the air inside will be more dense
C. The balloon will get bigger and the air inside will be more dense
D. The balloon will get smaller and the air inside will be less dense
Answer: B. The balloon will get smaller and the air inside will be more dense
Rationale: As water pressure increases, the volume of an air space decreases. This
causes the density of the air inside to increase as molecules are pushed closer
together.
8. If I am not able to equalize (clear) my body air spaces, it may be because I have:
A. Seasickness
B. Heart disease and high blood pressure
C. A cold, allergy, or another medical problem
D. Anxiety
Answer: C. A cold, allergy, or another medical problem
Rationale: A cold or congestion can block air passages in the ears and sinuses,
making equalization difficult or impossible. Divers should cancel a dive if they are
congested.
9. If my ears or sinuses hurt while I am descending (going down), it usually means:
A. My air spaces are equalized
B. My mask strap is too tight
C. I am feeling a squeeze and need to equalize
D. My mask is too small
Answer: C. I am feeling a squeeze and need to equalize
Rationale: Pain in the ears or sinuses during descent means they aren't equalized.
The diver should stop the descent, ascend slightly to relieve pressure, and attempt
to equalize again. If unable, the dive should be ended.
10. Lung overexpansion injuries can be caused by:
A. Scuba diving without a buddy
B. Continuing a dive when not properly weighted
C. Not drinking enough water before scuba diving
D. Holding my breath while scuba diving
Answer: D. Holding my breath while scuba diving
Rationale: Blocking off the lungs by holding the breath and ascending could cause
them to overexpand and rupture, which is a serious injury that could result in
paralysis and death.
, 11. If my cylinder of air lasts 60 minutes while I am at the surface breathing
normally, how long will it last at 20 meters (66 feet) breathing normally?
A. 60 minutes
B. 20 minutes
C. 15 minutes
D. 12 minutes
Answer: B. 20 minutes
Rationale: At 20 meters, pressure is 3 ATA (1 atm surface + 2 atm water). Air
consumption increases proportionally, so the tank will last 60/3 = 20 minutes.
12. The best place for me to position an alternate air source is:
A. Loose by my side so I can find it fast
B. In the triangle area formed by my chin and the lower corners of my rib cage
C. To the base of my cylinder
D. To the back of my BCD between my shoulder blades and waist
Answer: B. In the triangle area formed by my chin and the lower corners of my rib
cage
Rationale: The alternate air source should be secured with a quick-release in the
triangle area formed by the chin and the lower corners of the rib cage. It should
never dangle unsecured from the kit.
13. How often should I take my scuba cylinder to be visually inspected by my dive
center?
A. Once a year
B. Once every two years
C. Every six months
D. Every five years
Answer: A. Once a year
Rationale: Scuba cylinders require an annual visual inspection for internal
corrosion or other contamination or damage. A hydrostatic test is required every
five years.
14. The difference between DIN valves and yoke valves is that DIN valves:
A. Are made from durable plastic
B. Contain a spring-operated shutoff valve held open by cylinder pressure
C. Have an o-ring in them
D. Have threaded openings to screw the regulator into
Answer: D. Have threaded openings to screw the regulator into
