SSI OPEN WATER DIVER FINAL EXAM
250 UNIQUE MULTIPLE-CHOICE
QUESTIONS AND ANSWERS WITH
DETAILED RATIONALES LATEST
UPDATE 2026
---
SECTION 1: DIVING PHYSICS (Questions 1–50)
---
Question 1
A diver descends to 66 feet (20 meters) in saltwater. What is the absolute pressure
at this depth?
A) 2 atmospheres absolute (ata)
B) 3 atmospheres absolute (ata)
C) 4 atmospheres absolute (ata)
D) 1.5 atmospheres absolute (ata)
Correct Answer: B
,Rationale: In saltwater, pressure increases by 1 atmosphere (1 ata) for every 33 feet
(10 meters) of depth. At the surface, the absolute pressure is 1 ata. At 66 feet, the
water column exerts 2 ata of pressure (66 ft ÷ 33 ft/ata = 2). Absolute pressure is
the sum of atmospheric pressure and water pressure (1 ata + 2 ata = 3 ata). Option
A represents the pressure at 33 feet. Option C represents 99 feet.
---
Question 2
According to Boyle's Law, if a diver takes a full breath from a scuba tank at 66 feet
(20 meters) and ascends to the surface without exhaling, the volume of air in their
lungs would:
A) Remain the same
B) Decrease to one-third the original volume
C) Increase to three times the original volume
D) Increase to twice the original volume
Correct Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely proportional
(P₁V₁ = P₂V₂) at a constant temperature. At 66 feet (3 ata), the lung volume is
compressed. Upon ascending to the surface (1 ata), the pressure is reduced by a
factor of three. Consequently, the gas volume expands to three times its volume at
depth. This expansion creates a severe risk of lung overexpansion injury
(barotrauma). Option D would be correct for an ascent from 33 feet (2 ata).
---
,Question 3
A diver's buoyancy is determined by which of the following physical principles?
A) Boyle's Law
B) Charles's Law
C) Archimedes' Principle
D) Dalton's Law
Correct Answer: C
Rationale: Archimedes' Principle states that an object immersed in a fluid is
buoyed up by a force equal to the weight of the fluid displaced by the object. This
principle explains why objects float or sink and is the basis for determining a
diver's need for weight and buoyancy compensation. Boyle's Law relates to
pressure and volume, while Dalton's Law relates to partial pressures of gases.
---
Question 4
What is the partial pressure of oxygen (PPO₂) in a scuba tank filled with
compressed air (21% oxygen) at a depth of 99 feet (30 meters)?
A) 0.21 ata
B) 0.63 ata
C) 0.84 ata
D) 1.05 ata
, Correct Answer: C
Rationale: Dalton's Law states that the partial pressure of a gas is equal to the total
absolute pressure multiplied by the fraction of the gas. At 99 feet, the absolute
pressure is 4 ata (1 ata surface + 3 ata water). The calculation is: 4 ata × 0.21
(fraction of O₂) = 0.84 ata. Option A is the partial pressure at the surface. Option B
is the partial pressure at 66 feet (3 ata).
---
Question 5
One atmosphere of pressure is defined as:
A) Each 34 feet of depth in freshwater
B) Each 33 feet of depth in saltwater
C) 1 ata
D) All answers are correct
Correct Answer: D
Rationale: One atmosphere of pressure can be defined in multiple ways: as 1 ata
(atmosphere absolute), as the pressure exerted by 33 feet of seawater, or as the
pressure exerted by 34 feet of freshwater. All of these definitions are correct and
equivalent.
---
Question 6
250 UNIQUE MULTIPLE-CHOICE
QUESTIONS AND ANSWERS WITH
DETAILED RATIONALES LATEST
UPDATE 2026
---
SECTION 1: DIVING PHYSICS (Questions 1–50)
---
Question 1
A diver descends to 66 feet (20 meters) in saltwater. What is the absolute pressure
at this depth?
A) 2 atmospheres absolute (ata)
B) 3 atmospheres absolute (ata)
C) 4 atmospheres absolute (ata)
D) 1.5 atmospheres absolute (ata)
Correct Answer: B
,Rationale: In saltwater, pressure increases by 1 atmosphere (1 ata) for every 33 feet
(10 meters) of depth. At the surface, the absolute pressure is 1 ata. At 66 feet, the
water column exerts 2 ata of pressure (66 ft ÷ 33 ft/ata = 2). Absolute pressure is
the sum of atmospheric pressure and water pressure (1 ata + 2 ata = 3 ata). Option
A represents the pressure at 33 feet. Option C represents 99 feet.
---
Question 2
According to Boyle's Law, if a diver takes a full breath from a scuba tank at 66 feet
(20 meters) and ascends to the surface without exhaling, the volume of air in their
lungs would:
A) Remain the same
B) Decrease to one-third the original volume
C) Increase to three times the original volume
D) Increase to twice the original volume
Correct Answer: C
Rationale: Boyle's Law states that pressure and volume are inversely proportional
(P₁V₁ = P₂V₂) at a constant temperature. At 66 feet (3 ata), the lung volume is
compressed. Upon ascending to the surface (1 ata), the pressure is reduced by a
factor of three. Consequently, the gas volume expands to three times its volume at
depth. This expansion creates a severe risk of lung overexpansion injury
(barotrauma). Option D would be correct for an ascent from 33 feet (2 ata).
---
,Question 3
A diver's buoyancy is determined by which of the following physical principles?
A) Boyle's Law
B) Charles's Law
C) Archimedes' Principle
D) Dalton's Law
Correct Answer: C
Rationale: Archimedes' Principle states that an object immersed in a fluid is
buoyed up by a force equal to the weight of the fluid displaced by the object. This
principle explains why objects float or sink and is the basis for determining a
diver's need for weight and buoyancy compensation. Boyle's Law relates to
pressure and volume, while Dalton's Law relates to partial pressures of gases.
---
Question 4
What is the partial pressure of oxygen (PPO₂) in a scuba tank filled with
compressed air (21% oxygen) at a depth of 99 feet (30 meters)?
A) 0.21 ata
B) 0.63 ata
C) 0.84 ata
D) 1.05 ata
, Correct Answer: C
Rationale: Dalton's Law states that the partial pressure of a gas is equal to the total
absolute pressure multiplied by the fraction of the gas. At 99 feet, the absolute
pressure is 4 ata (1 ata surface + 3 ata water). The calculation is: 4 ata × 0.21
(fraction of O₂) = 0.84 ata. Option A is the partial pressure at the surface. Option B
is the partial pressure at 66 feet (3 ata).
---
Question 5
One atmosphere of pressure is defined as:
A) Each 34 feet of depth in freshwater
B) Each 33 feet of depth in saltwater
C) 1 ata
D) All answers are correct
Correct Answer: D
Rationale: One atmosphere of pressure can be defined in multiple ways: as 1 ata
(atmosphere absolute), as the pressure exerted by 33 feet of seawater, or as the
pressure exerted by 34 feet of freshwater. All of these definitions are correct and
equivalent.
---
Question 6
