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BSAC Sports Diver Theory Actual Exam
2026/2027 – Complete Exam-Style Questions
with Detailed Rationales | 100% Verified |
Pass Guaranteed – A+ Graded
[SECTION 1: Diving Physics & Physiology — Questions 1-20]
Q1: According to Boyle's Law, if a diver holds their breath while ascending from 10 meters to
the surface, the volume of air in their lungs will:
A. Decrease by half.
B. Remain constant.
C. Double.
D. Triple.
Correct Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely proportional at a constant
temperature (P1V1 = P2V2). At 10 meters, the ambient pressure is 2 bar (ata), and at the surface,
it is 1 bar. Therefore, as pressure halves, the volume doubles. This expansion can cause lung
over-expansion injury (pulmonary barotrauma) if the air is trapped, which is why divers must
never hold their breath during ascent.
Q2: What is the physiological reason for "mask squeeze" during a descent?
A. Boyle's Law causing the volume of air in the mask to decrease, creating a vacuum.
B. Failure to exhale into the mask to equalize pressure.
C. Henry's Law causing gas to dissolve into the facial tissues.
D. Dalton's Law causing oxygen toxicity in the sinus cavities.
Correct Answer: B
,2
Rationale: As a diver descends, the increasing ambient pressure (Boyle's Law) reduces the
volume of the air space inside the mask. If the diver does not exhale nasally into the mask to add
air and equalize the pressure, the pressure differential sucks the mask against the face, causing
capillary rupture and bruising (ecchymosis).
Q3: A diver breathing air at a depth of 40 meters (5 bar) is breathing a gas mixture. What is the
Partial Pressure of Oxygen (PO2) in their lungs?
A. 0.21 bar
B. 1.0 bar
C. 1.05 bar
D. 5.0 bar
Correct Answer: C
Rationale: Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the
partial pressures of the individual gases. The formula is Ptotal × Fraction of Gas = Pgas. At 40
meters (5 bar), 5 bar × 0.21 (21% oxygen in air) = 1.05 bar. This is well within the safe
recreational limit of 1.4 bar.
Q4: Which gas law explains why Nitrogen dissolves into the body tissues during a dive?
A. Boyle's Law
B. Dalton's Law
C. Henry's Law
D. Charles's Law
Correct Answer: C
Rationale: Henry's Law states that the amount of gas dissolved in a liquid is directly proportional
to the partial pressure of that gas above the liquid. As a diver breathes air under pressure, the
partial pressure of nitrogen increases in the lungs, causing more nitrogen to dissolve into the
blood and tissues (on-gassing). This is the underlying principle of decompression sickness
(DCS).
,3
Q5: A Sports Diver plans to dive to a maximum depth of 35 meters. According to BSAC
recommendations, what is the maximum working Partial Pressure of Oxygen (PO2) allowed for
sport diving?
A. 1.0 bar
B. 1.4 bar
C. 1.6 bar
D. 2.0 bar
Correct Answer: B
Rationale: BSAC generally follows the technical diving standard of a maximum working PO2 of
1.4 bar to minimize the risk of Central Nervous System (CNS) oxygen toxicity. A limit of 1.6 bar
is often reserved for decompression stops or contingency, but 1.4 bar is the standard safe
operating limit for the dive phase to reduce the risk of convulsions underwater.
Q6: Which of the following is a symptom of CNS (Central Nervous System) Oxygen Toxicity?
A. Joint pain
B. Itchy skin
C. Tunnel vision
D. Sore throat
Correct Answer: C
Rationale: Symptoms of CNS oxygen toxicity can be remembered by the acronym
CONVULSIONS, but early signs include visual disturbances such as tunnel vision, nausea,
tinnitus, twitching (especially of the lips), and irritability. Joint pain is a sign of DCS, and itchy
skin is a sign of pulmonary oxygen toxicity or DCS skin bends.
Q7: Archimedes' Principle states that an object immersed in a fluid is buoyed up by a force equal
to:
A. The weight of the object.
B. The weight of the fluid displaced.
, 4
C. The volume of the fluid displaced.
D. The pressure at the depth of the object.
Correct Answer: B
Rationale: Archimedes' Principle explains buoyancy: an object will float or sink based on
whether it weighs more or less than the water it displaces. If the weight of the displaced water is
greater than the object's weight, the object is positively buoyant. This is fundamental for divers
calculating their weighting requirements.
Q8: Why is "Silent Bubble" formation a concern for divers, particularly when flying after
diving?
A. They are harmless noise made by the regulator.
B. They are asymptomatic nitrogen bubbles that can grow if ambient pressure decreases (e.g., in
an aircraft).
C. They are bubbles caused by hyperventilation.
D. They indicate a failure of the BCD inflator mechanism.
Correct Answer: B
Rationale: "Silent bubbles" are microscopic nitrogen bubbles often present in the bloodstream
after a dive even without symptoms of DCS. If a diver flies immediately, the reduced cabin
pressure causes these bubbles to expand according to Boyle's Law, potentially growing large
enough to cause symptoms of Decompression Sickness. This is why a surface interval is required
before flying.
Q9: Which of the following factors increases the risk of Decompression Sickness (DCS)?
A. Drinking plenty of water before diving.
B. Making a safety stop at 6 meters.
C. Being obese.
D. Exercising moderately the night before.
BSAC Sports Diver Theory Actual Exam
2026/2027 – Complete Exam-Style Questions
with Detailed Rationales | 100% Verified |
Pass Guaranteed – A+ Graded
[SECTION 1: Diving Physics & Physiology — Questions 1-20]
Q1: According to Boyle's Law, if a diver holds their breath while ascending from 10 meters to
the surface, the volume of air in their lungs will:
A. Decrease by half.
B. Remain constant.
C. Double.
D. Triple.
Correct Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely proportional at a constant
temperature (P1V1 = P2V2). At 10 meters, the ambient pressure is 2 bar (ata), and at the surface,
it is 1 bar. Therefore, as pressure halves, the volume doubles. This expansion can cause lung
over-expansion injury (pulmonary barotrauma) if the air is trapped, which is why divers must
never hold their breath during ascent.
Q2: What is the physiological reason for "mask squeeze" during a descent?
A. Boyle's Law causing the volume of air in the mask to decrease, creating a vacuum.
B. Failure to exhale into the mask to equalize pressure.
C. Henry's Law causing gas to dissolve into the facial tissues.
D. Dalton's Law causing oxygen toxicity in the sinus cavities.
Correct Answer: B
,2
Rationale: As a diver descends, the increasing ambient pressure (Boyle's Law) reduces the
volume of the air space inside the mask. If the diver does not exhale nasally into the mask to add
air and equalize the pressure, the pressure differential sucks the mask against the face, causing
capillary rupture and bruising (ecchymosis).
Q3: A diver breathing air at a depth of 40 meters (5 bar) is breathing a gas mixture. What is the
Partial Pressure of Oxygen (PO2) in their lungs?
A. 0.21 bar
B. 1.0 bar
C. 1.05 bar
D. 5.0 bar
Correct Answer: C
Rationale: Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the
partial pressures of the individual gases. The formula is Ptotal × Fraction of Gas = Pgas. At 40
meters (5 bar), 5 bar × 0.21 (21% oxygen in air) = 1.05 bar. This is well within the safe
recreational limit of 1.4 bar.
Q4: Which gas law explains why Nitrogen dissolves into the body tissues during a dive?
A. Boyle's Law
B. Dalton's Law
C. Henry's Law
D. Charles's Law
Correct Answer: C
Rationale: Henry's Law states that the amount of gas dissolved in a liquid is directly proportional
to the partial pressure of that gas above the liquid. As a diver breathes air under pressure, the
partial pressure of nitrogen increases in the lungs, causing more nitrogen to dissolve into the
blood and tissues (on-gassing). This is the underlying principle of decompression sickness
(DCS).
,3
Q5: A Sports Diver plans to dive to a maximum depth of 35 meters. According to BSAC
recommendations, what is the maximum working Partial Pressure of Oxygen (PO2) allowed for
sport diving?
A. 1.0 bar
B. 1.4 bar
C. 1.6 bar
D. 2.0 bar
Correct Answer: B
Rationale: BSAC generally follows the technical diving standard of a maximum working PO2 of
1.4 bar to minimize the risk of Central Nervous System (CNS) oxygen toxicity. A limit of 1.6 bar
is often reserved for decompression stops or contingency, but 1.4 bar is the standard safe
operating limit for the dive phase to reduce the risk of convulsions underwater.
Q6: Which of the following is a symptom of CNS (Central Nervous System) Oxygen Toxicity?
A. Joint pain
B. Itchy skin
C. Tunnel vision
D. Sore throat
Correct Answer: C
Rationale: Symptoms of CNS oxygen toxicity can be remembered by the acronym
CONVULSIONS, but early signs include visual disturbances such as tunnel vision, nausea,
tinnitus, twitching (especially of the lips), and irritability. Joint pain is a sign of DCS, and itchy
skin is a sign of pulmonary oxygen toxicity or DCS skin bends.
Q7: Archimedes' Principle states that an object immersed in a fluid is buoyed up by a force equal
to:
A. The weight of the object.
B. The weight of the fluid displaced.
, 4
C. The volume of the fluid displaced.
D. The pressure at the depth of the object.
Correct Answer: B
Rationale: Archimedes' Principle explains buoyancy: an object will float or sink based on
whether it weighs more or less than the water it displaces. If the weight of the displaced water is
greater than the object's weight, the object is positively buoyant. This is fundamental for divers
calculating their weighting requirements.
Q8: Why is "Silent Bubble" formation a concern for divers, particularly when flying after
diving?
A. They are harmless noise made by the regulator.
B. They are asymptomatic nitrogen bubbles that can grow if ambient pressure decreases (e.g., in
an aircraft).
C. They are bubbles caused by hyperventilation.
D. They indicate a failure of the BCD inflator mechanism.
Correct Answer: B
Rationale: "Silent bubbles" are microscopic nitrogen bubbles often present in the bloodstream
after a dive even without symptoms of DCS. If a diver flies immediately, the reduced cabin
pressure causes these bubbles to expand according to Boyle's Law, potentially growing large
enough to cause symptoms of Decompression Sickness. This is why a surface interval is required
before flying.
Q9: Which of the following factors increases the risk of Decompression Sickness (DCS)?
A. Drinking plenty of water before diving.
B. Making a safety stop at 6 meters.
C. Being obese.
D. Exercising moderately the night before.
