SSI SCIENCE OF DIVING 2027 STUDY GUIDE
1. Which statement best describes the primary objective of
understanding the science of diving?
A. To increase underwater swimming speed only
B. To understand how pressure, gases, physiology, and equipment
interact for safe diving
C. To eliminate all diving risks completely
D. To allow divers to exceed recreational depth limits safely
Answer: B
Rationale: The science of diving integrates physics, physiology,
chemistry, environmental science, and equipment operation to
explain how the underwater environment affects the human body.
This knowledge enables divers to prevent injuries, recognize hazards,
and make informed decisions before, during, and after dives.
2. According to Boyle's Law, what happens to the volume of air in a
flexible container as ambient pressure doubles?
A. The volume doubles
B. The volume remains constant
C. The volume decreases by half
D. The volume triples
Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely
proportional when temperature remains constant. Doubling pressure
reduces gas volume to one-half. This principle explains mask squeeze,
1|Page
,lung overexpansion injuries, and buoyancy changes during ascent and
descent.
3. A diver descends from the surface to 10 meters (33 feet) in
seawater. Approximately what is the ambient pressure?
A. 1 atmosphere absolute (ATA)
B. 1.5 ATA
C. 2 ATA
D. 3 ATA
Answer: C
Rationale: Atmospheric pressure at sea level is approximately 1 ATA.
Every 10 meters (33 feet) of seawater adds another ATA, making the
total pressure at 10 meters approximately 2 ATA.
4. Which gas law best explains why dissolved nitrogen enters body
tissues during a dive?
A. Boyle's Law
B. Charles's Law
C. Dalton's Law
D. Henry's Law
Answer: D
Rationale: Henry's Law states that the amount of gas dissolved in a
liquid increases with increasing pressure. During descent, elevated
2|Page
,pressure causes more nitrogen to dissolve into blood and tissues,
forming the basis for decompression theory.
5. Dalton's Law of Partial Pressures states that:
A. Pressure decreases with depth.
B. Each gas contributes independently to the total pressure of a gas
mixture.
C. Gas volume increases with pressure.
D. Water pressure is unrelated to breathing gas.
Answer: B
Rationale: Dalton's Law explains that each gas in a mixture exerts its
own partial pressure. Understanding partial pressures is essential
when discussing oxygen toxicity, nitrogen narcosis, and mixed-gas
diving.
6. Which breathing gas normally comprises approximately 78% of
atmospheric air?
A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Argon
Answer: C
Rationale: Atmospheric air contains roughly 78% nitrogen, 21%
oxygen, and small amounts of argon, carbon dioxide, and trace gases.
3|Page
, Nitrogen plays a central role in decompression sickness and nitrogen
narcosis.
7. Why should a diver never hold their breath while ascending?
A. Oxygen levels rise too quickly.
B. Lung air expands as pressure decreases, potentially causing lung
overexpansion injuries.
C. Carbon dioxide disappears immediately.
D. Water pressure increases rapidly.
Answer: B
Rationale: Expanding air follows Boyle's Law. Holding one's breath
prevents expanding gas from escaping, potentially rupturing lung
tissue and allowing gas bubbles to enter the bloodstream, resulting in
arterial gas embolism.
8. Which body air space is considered non-flexible and must be
equalized during descent?
A. Blood vessels
B. Middle ear
C. Muscle tissue
D. Bones
Answer: B
4|Page
1. Which statement best describes the primary objective of
understanding the science of diving?
A. To increase underwater swimming speed only
B. To understand how pressure, gases, physiology, and equipment
interact for safe diving
C. To eliminate all diving risks completely
D. To allow divers to exceed recreational depth limits safely
Answer: B
Rationale: The science of diving integrates physics, physiology,
chemistry, environmental science, and equipment operation to
explain how the underwater environment affects the human body.
This knowledge enables divers to prevent injuries, recognize hazards,
and make informed decisions before, during, and after dives.
2. According to Boyle's Law, what happens to the volume of air in a
flexible container as ambient pressure doubles?
A. The volume doubles
B. The volume remains constant
C. The volume decreases by half
D. The volume triples
Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely
proportional when temperature remains constant. Doubling pressure
reduces gas volume to one-half. This principle explains mask squeeze,
1|Page
,lung overexpansion injuries, and buoyancy changes during ascent and
descent.
3. A diver descends from the surface to 10 meters (33 feet) in
seawater. Approximately what is the ambient pressure?
A. 1 atmosphere absolute (ATA)
B. 1.5 ATA
C. 2 ATA
D. 3 ATA
Answer: C
Rationale: Atmospheric pressure at sea level is approximately 1 ATA.
Every 10 meters (33 feet) of seawater adds another ATA, making the
total pressure at 10 meters approximately 2 ATA.
4. Which gas law best explains why dissolved nitrogen enters body
tissues during a dive?
A. Boyle's Law
B. Charles's Law
C. Dalton's Law
D. Henry's Law
Answer: D
Rationale: Henry's Law states that the amount of gas dissolved in a
liquid increases with increasing pressure. During descent, elevated
2|Page
,pressure causes more nitrogen to dissolve into blood and tissues,
forming the basis for decompression theory.
5. Dalton's Law of Partial Pressures states that:
A. Pressure decreases with depth.
B. Each gas contributes independently to the total pressure of a gas
mixture.
C. Gas volume increases with pressure.
D. Water pressure is unrelated to breathing gas.
Answer: B
Rationale: Dalton's Law explains that each gas in a mixture exerts its
own partial pressure. Understanding partial pressures is essential
when discussing oxygen toxicity, nitrogen narcosis, and mixed-gas
diving.
6. Which breathing gas normally comprises approximately 78% of
atmospheric air?
A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Argon
Answer: C
Rationale: Atmospheric air contains roughly 78% nitrogen, 21%
oxygen, and small amounts of argon, carbon dioxide, and trace gases.
3|Page
, Nitrogen plays a central role in decompression sickness and nitrogen
narcosis.
7. Why should a diver never hold their breath while ascending?
A. Oxygen levels rise too quickly.
B. Lung air expands as pressure decreases, potentially causing lung
overexpansion injuries.
C. Carbon dioxide disappears immediately.
D. Water pressure increases rapidly.
Answer: B
Rationale: Expanding air follows Boyle's Law. Holding one's breath
prevents expanding gas from escaping, potentially rupturing lung
tissue and allowing gas bubbles to enter the bloodstream, resulting in
arterial gas embolism.
8. Which body air space is considered non-flexible and must be
equalized during descent?
A. Blood vessels
B. Middle ear
C. Muscle tissue
D. Bones
Answer: B
4|Page
