PADI Open Water Diver | Comprehensive Study
Guide, Practice Exam, Questions & Answers,
Exam Prep Test Bank, Scuba Diving
Fundamentals, Dive Planning, Underwater
Navigation, Diving Equipment, Dive Safety,
Buoyancy Control, Emergency Procedures,
Marine Environment, Detailed Rationales,
Complete Review
Question 1: What is the maximum depth a PADI Open Water Diver is certified
to dive?
A. 12 meters/40 feet
B. 18 meters/60 feet
C. 30 meters/100 feet
D. 40 meters/130 feet
CORRECT ANSWER: B. 18 meters/60 feet
Rationale: The PADI Open Water Diver course certifies divers to a maximum depth of
18 meters/60 feet, or the actual depth reached during training if shallower. This depth
limit is established to ensure the safety of entry-level divers within recreational dive
limits .
Question 2: If an object is neutrally buoyant in fresh water, what would
happen to it in salt water?
A. It would sink.
B. It would float.
C. It would remain neutrally buoyant.
D. It would first sink and then float.
CORRECT ANSWER: B. It would float.
Rationale: Salt water is denser than fresh water due to dissolved minerals, which creates
greater upward force (buoyancy) on an object. An object that is neutrally buoyant in
fresh water would therefore float in salt water .
Question 3: A diver takes a balloon filled with air from the surface to the
bottom of a 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.
,CORRECT ANSWER: B. The balloon will get smaller and the air inside will be
more dense.
Rationale: As water pressure increases with depth, the volume of a flexible air space
decreases. This compression causes the air molecules to move closer together, resulting
in increased density of the air inside the balloon .
Question 4: A diver traps air in a glass and takes it down to 10 meters/33 feet.
What happens to the air space?
A. It becomes half the size it was at the surface.
B. It becomes one-third the size it was at the surface.
C. It remains the same size.
D. It becomes two-thirds the size it was at the surface.
CORRECT ANSWER: A. It becomes half the size it was at the surface.
Rationale: At 10 meters/33 feet, the absolute pressure is 2 bar/ata (1 atmosphere from
the surface plus 1 atmosphere from the water). According to Boyle's Law, the volume of
a gas is inversely proportional to pressure, so the air space would be reduced to half its
original surface volume .
Question 5: A diver is unable to equalize (clear) their ears and sinuses during
descent. Which of the following is the most likely cause?
A. Seasickness
B. Heart disease
C. A cold, allergy, or other medical condition causing congestion
D. Anxiety
CORRECT ANSWER: C. A cold, allergy, or other medical condition causing
congestion
Rationale: A cold, allergy, or other condition that causes nasal or sinus congestion can
block the air passages (Eustachian tubes) that connect the middle ear and sinuses to the
throat. This makes equalization difficult or impossible, preventing the diver from
balancing pressure in these air spaces during descent .
Question 6: A diver experiences ear or sinus pain while descending. What does
this most likely indicate?
A. They are properly equalized.
B. Their mask strap is too tight.
C. They are feeling a squeeze and need to equalize.
D. Their mask is too small.
CORRECT ANSWER: C. They are feeling a squeeze and need to equalize.
Rationale: Pain in the ears or sinuses during descent is a classic symptom of a "squeeze,"
which occurs when the pressure in these air spaces is not equalized with the increasing
,ambient water pressure. The diver should stop their descent, ascend slightly to reduce
the pressure differential, and attempt to equalize again .
Question 7: What is the best location to position an alternate air source on a
diver's equipment?
A. Loose by their side for quick access.
B. In the triangle area formed by the chin and the lower corners of the rib cage.
C. Attached to the base of the cylinder.
D. On the back of the BCD between the shoulder blades and waist.
CORRECT ANSWER: B. In the triangle area formed by the chin and the lower
corners of the rib cage.
Rationale: The alternate air source should be secured in the "triangle area" (from the
chin to the lower corners of the rib cage). This central, accessible position makes it easy
for the diver to find and for a buddy to access in an out-of-air emergency. It should not
be left dangling loose, as it could drag or become entangled .
Question 8: Lung overexpansion injuries in scuba diving are most directly
caused by which of the following actions?
A. Diving without a buddy.
B. Continuing a dive when not properly weighted.
C. Not drinking enough water.
D. Holding one's breath while scuba diving.
CORRECT ANSWER: D. Holding one's breath while scuba diving.
Rationale: Holding one's breath while ascending is the primary cause of lung
overexpansion injuries. As a diver ascends, the pressure decreases, causing the air in the
lungs to expand. If the airway is blocked (by holding the breath), the expanding air can
over-expand and rupture the lung tissue, leading to serious injury .
Question 9: A scuba cylinder that lasts 60 minutes at the surface will last
approximately how long at a depth of 20 meters/66 feet, assuming all else
remains the same?
A. 60 minutes
B. 20 minutes
C. 15 minutes
D. 12 minutes
CORRECT ANSWER: B. 20 minutes
Rationale: At 20 meters/66 feet, the absolute pressure is 3 bar/ata (1 atmosphere at the
surface + 2 atmospheres from the water). A diver breathes air at a rate proportional to
the ambient pressure. Therefore, the air consumption rate is three times higher than at
the surface, and the cylinder will last 60 minutes / 3 = 20 minutes .
, Question 10: How often should a scuba cylinder undergo a visual inspection by
a dive center?
A. Once a year.
B. Once every two years.
C. Every six months.
D. Every five years.
CORRECT ANSWER: A. Once a year.
Rationale: PADI and industry standards recommend that scuba cylinders undergo a
visual inspection annually. This inspection is performed by a qualified technician to
check for internal corrosion, damage, or other contamination that could compromise the
cylinder's safety .
Question 11: What is the primary difference between a DIN valve and a Yoke
(K-valve) valve on a scuba cylinder?
A. DIN valves are made of plastic, while Yoke valves are metal.
B. DIN valves have a built-in pressure gauge.
C. DIN valves have a spring-operated shutoff valve.
D. DIN valves have threaded openings to screw the regulator into.
CORRECT ANSWER: D. DIN valves have threaded openings to screw the
regulator into.
Rationale: The key difference is the connection method. A DIN (Deutsche Industrie
Norm) valve has a threaded opening that the regulator first stage screws directly into. A
Yoke valve uses a clamp (yoke) that fits over the valve's O-ring to secure the regulator,
which is a different connection system .
Question 12: Which of the following is a correct practice for the proper care of
a scuba cylinder?
A. Sand and repaint it every year.
B. Dry it in the sun.
C. Keep some air in it.
D. Have it pressure tested every month.
CORRECT ANSWER: C. Keep some air in it.
Rationale: Keeping a small amount of air (around 200 psi/14 bar) in a scuba cylinder
helps prevent moisture from entering and causing internal corrosion. The cylinder
should also be stored upright in a safe place away from high heat. Hydrostatic pressure
testing is required at longer intervals (typically every 2-5 years), not monthly .
Question 13: When a diver looks at objects underwater, they often appear
________ than they do on the surface.
A. larger and/or nearer
B. larger and/or further away
Guide, Practice Exam, Questions & Answers,
Exam Prep Test Bank, Scuba Diving
Fundamentals, Dive Planning, Underwater
Navigation, Diving Equipment, Dive Safety,
Buoyancy Control, Emergency Procedures,
Marine Environment, Detailed Rationales,
Complete Review
Question 1: What is the maximum depth a PADI Open Water Diver is certified
to dive?
A. 12 meters/40 feet
B. 18 meters/60 feet
C. 30 meters/100 feet
D. 40 meters/130 feet
CORRECT ANSWER: B. 18 meters/60 feet
Rationale: The PADI Open Water Diver course certifies divers to a maximum depth of
18 meters/60 feet, or the actual depth reached during training if shallower. This depth
limit is established to ensure the safety of entry-level divers within recreational dive
limits .
Question 2: If an object is neutrally buoyant in fresh water, what would
happen to it in salt water?
A. It would sink.
B. It would float.
C. It would remain neutrally buoyant.
D. It would first sink and then float.
CORRECT ANSWER: B. It would float.
Rationale: Salt water is denser than fresh water due to dissolved minerals, which creates
greater upward force (buoyancy) on an object. An object that is neutrally buoyant in
fresh water would therefore float in salt water .
Question 3: A diver takes a balloon filled with air from the surface to the
bottom of a 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.
,CORRECT ANSWER: B. The balloon will get smaller and the air inside will be
more dense.
Rationale: As water pressure increases with depth, the volume of a flexible air space
decreases. This compression causes the air molecules to move closer together, resulting
in increased density of the air inside the balloon .
Question 4: A diver traps air in a glass and takes it down to 10 meters/33 feet.
What happens to the air space?
A. It becomes half the size it was at the surface.
B. It becomes one-third the size it was at the surface.
C. It remains the same size.
D. It becomes two-thirds the size it was at the surface.
CORRECT ANSWER: A. It becomes half the size it was at the surface.
Rationale: At 10 meters/33 feet, the absolute pressure is 2 bar/ata (1 atmosphere from
the surface plus 1 atmosphere from the water). According to Boyle's Law, the volume of
a gas is inversely proportional to pressure, so the air space would be reduced to half its
original surface volume .
Question 5: A diver is unable to equalize (clear) their ears and sinuses during
descent. Which of the following is the most likely cause?
A. Seasickness
B. Heart disease
C. A cold, allergy, or other medical condition causing congestion
D. Anxiety
CORRECT ANSWER: C. A cold, allergy, or other medical condition causing
congestion
Rationale: A cold, allergy, or other condition that causes nasal or sinus congestion can
block the air passages (Eustachian tubes) that connect the middle ear and sinuses to the
throat. This makes equalization difficult or impossible, preventing the diver from
balancing pressure in these air spaces during descent .
Question 6: A diver experiences ear or sinus pain while descending. What does
this most likely indicate?
A. They are properly equalized.
B. Their mask strap is too tight.
C. They are feeling a squeeze and need to equalize.
D. Their mask is too small.
CORRECT ANSWER: C. They are feeling a squeeze and need to equalize.
Rationale: Pain in the ears or sinuses during descent is a classic symptom of a "squeeze,"
which occurs when the pressure in these air spaces is not equalized with the increasing
,ambient water pressure. The diver should stop their descent, ascend slightly to reduce
the pressure differential, and attempt to equalize again .
Question 7: What is the best location to position an alternate air source on a
diver's equipment?
A. Loose by their side for quick access.
B. In the triangle area formed by the chin and the lower corners of the rib cage.
C. Attached to the base of the cylinder.
D. On the back of the BCD between the shoulder blades and waist.
CORRECT ANSWER: B. In the triangle area formed by the chin and the lower
corners of the rib cage.
Rationale: The alternate air source should be secured in the "triangle area" (from the
chin to the lower corners of the rib cage). This central, accessible position makes it easy
for the diver to find and for a buddy to access in an out-of-air emergency. It should not
be left dangling loose, as it could drag or become entangled .
Question 8: Lung overexpansion injuries in scuba diving are most directly
caused by which of the following actions?
A. Diving without a buddy.
B. Continuing a dive when not properly weighted.
C. Not drinking enough water.
D. Holding one's breath while scuba diving.
CORRECT ANSWER: D. Holding one's breath while scuba diving.
Rationale: Holding one's breath while ascending is the primary cause of lung
overexpansion injuries. As a diver ascends, the pressure decreases, causing the air in the
lungs to expand. If the airway is blocked (by holding the breath), the expanding air can
over-expand and rupture the lung tissue, leading to serious injury .
Question 9: A scuba cylinder that lasts 60 minutes at the surface will last
approximately how long at a depth of 20 meters/66 feet, assuming all else
remains the same?
A. 60 minutes
B. 20 minutes
C. 15 minutes
D. 12 minutes
CORRECT ANSWER: B. 20 minutes
Rationale: At 20 meters/66 feet, the absolute pressure is 3 bar/ata (1 atmosphere at the
surface + 2 atmospheres from the water). A diver breathes air at a rate proportional to
the ambient pressure. Therefore, the air consumption rate is three times higher than at
the surface, and the cylinder will last 60 minutes / 3 = 20 minutes .
, Question 10: How often should a scuba cylinder undergo a visual inspection by
a dive center?
A. Once a year.
B. Once every two years.
C. Every six months.
D. Every five years.
CORRECT ANSWER: A. Once a year.
Rationale: PADI and industry standards recommend that scuba cylinders undergo a
visual inspection annually. This inspection is performed by a qualified technician to
check for internal corrosion, damage, or other contamination that could compromise the
cylinder's safety .
Question 11: What is the primary difference between a DIN valve and a Yoke
(K-valve) valve on a scuba cylinder?
A. DIN valves are made of plastic, while Yoke valves are metal.
B. DIN valves have a built-in pressure gauge.
C. DIN valves have a spring-operated shutoff valve.
D. DIN valves have threaded openings to screw the regulator into.
CORRECT ANSWER: D. DIN valves have threaded openings to screw the
regulator into.
Rationale: The key difference is the connection method. A DIN (Deutsche Industrie
Norm) valve has a threaded opening that the regulator first stage screws directly into. A
Yoke valve uses a clamp (yoke) that fits over the valve's O-ring to secure the regulator,
which is a different connection system .
Question 12: Which of the following is a correct practice for the proper care of
a scuba cylinder?
A. Sand and repaint it every year.
B. Dry it in the sun.
C. Keep some air in it.
D. Have it pressure tested every month.
CORRECT ANSWER: C. Keep some air in it.
Rationale: Keeping a small amount of air (around 200 psi/14 bar) in a scuba cylinder
helps prevent moisture from entering and causing internal corrosion. The cylinder
should also be stored upright in a safe place away from high heat. Hydrostatic pressure
testing is required at longer intervals (typically every 2-5 years), not monthly .
Question 13: When a diver looks at objects underwater, they often appear
________ than they do on the surface.
A. larger and/or nearer
B. larger and/or further away
