Study Guide: SDI Scuba Certification Exam Study Guide:
Questions & Answers
What does SCUBA stand for? - ANSWER:Self
Contained
Underwater
Breathing
Apparatus
List the three important scuba diving changes that occurred in the 1950s - ANSWER:1) Dive tables
published for repetitive dives
2) Improved design/quality of scuba gear
3) Dive computers commercially available
Name three different devices that modern dive computers replace - ANSWER:Depth gauge, dive tables,
watch
What sets SDI apart from other training agencies? - ANSWER:Students use a personal dive computer for
all instruction and certification dives
How much larger and closer do objects appear under water and why? - ANSWER:33% larger, 25% closer
Light bends in the air-space between the lens and your eyes.
How much faster does sound move through water than air and why? - ANSWER:4 times faster in water
Water is 800x denser than air; sound travels through denser mediums at faster rates
What is the first color absorbed underwater? - ANSWER:RED (followed by OYGBIV)
When diving from shore, the best time to dive is when there is the least amount of tidal current. _____
tide is when there is no horizontal water movement. - ANSWER:Slack
If you are caught in a rip current, first swim _____ to the current to get out of it before swimming
towards shore. - ANSWER:Perpendicular
Start your dive by swimming ____ the current - ANSWER:into/against
Global currents are _____.-ANSWER:Fixed
Local currents ____. - ANSWER:Flactuate
Rip current - ANSWER:Current which goes seaward due to ocean floor stuctures
Long shore current - ANSWER:Flows parallel to shore
Waves are caused by - ANSWER:energy generated by WIND
, Tides are caused by - ANSWER:polarity of the moon
T/F: Anticipate surge action to avoid contact with stationary objects. - ANSWER:True
What is surge - ANSWER:Back and forth motion underwater which you shouldn't fight; move deeper and
away from dangerous objects if caught in one. USE THEM TO YOUR ADVANTAGE
What types of marine life cause most diving injuries - ANSWER:Jellyfish or marine life which account for
a temporary, painful sting. WATCH OUT FOR ALLERGIC REACTIONS.
Injuries due to marine life typically a _____ response - ANSWER:Defense
How do you treat a sting? - ANSWER:Hot water or vinegar
What should you do if a potentially dangerous animal underwater does not leave your area? -
ANSWER:Remain still
Remain calm
Slowly leave area
List three different reasons that it is advisable to check with your local dive center before diving in an
unfamiliar area. - ANSWER:1) Rip currents could be prevalent
2) Thermoclines could affect thermal protection
3) YOU ARE SUBJECT TO LOCALITY (be aware of laws and regulations
What is the absolute pressure in atm at 20m/66ft? - ANSWER:3 atm absolute
What will be the volume in a ball that is filled with 2 cubic feet of air at 30 m/99ft when it is taken to the
surface? - ANSWER:8 cubic feet
How many times more dense is air in a balloon at 4 atm compared to the air density at the surface? -
ANSWER:4 times
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? - ANSWER:40 min
How often should you equalize during descent? - ANSWER:Early and often; at the surface and then every
couple feet so no discomfort is felt
What should you do if you experience discomfort in your ears upon descending? - ANSWER:Immediately
stop descending and ascend a few feet until you are shallow enough not to feel any discomfort
What is reverse block? - ANSWER:Occurs when air cannot expand or escape freely when ascending
What should you do if you experience a reverse block upon ascending? - ANSWER:Descend a couple feet
and stay there until air has time to vent
What is the most important rule in scuba diving? - ANSWER:Do not hold your breath, breathe
continuously
What is the most serious injury that a diver could suffer from if they hold their breathe upon ascending?
- ANSWER:Lung overexpansion injuries
Questions & Answers
What does SCUBA stand for? - ANSWER:Self
Contained
Underwater
Breathing
Apparatus
List the three important scuba diving changes that occurred in the 1950s - ANSWER:1) Dive tables
published for repetitive dives
2) Improved design/quality of scuba gear
3) Dive computers commercially available
Name three different devices that modern dive computers replace - ANSWER:Depth gauge, dive tables,
watch
What sets SDI apart from other training agencies? - ANSWER:Students use a personal dive computer for
all instruction and certification dives
How much larger and closer do objects appear under water and why? - ANSWER:33% larger, 25% closer
Light bends in the air-space between the lens and your eyes.
How much faster does sound move through water than air and why? - ANSWER:4 times faster in water
Water is 800x denser than air; sound travels through denser mediums at faster rates
What is the first color absorbed underwater? - ANSWER:RED (followed by OYGBIV)
When diving from shore, the best time to dive is when there is the least amount of tidal current. _____
tide is when there is no horizontal water movement. - ANSWER:Slack
If you are caught in a rip current, first swim _____ to the current to get out of it before swimming
towards shore. - ANSWER:Perpendicular
Start your dive by swimming ____ the current - ANSWER:into/against
Global currents are _____.-ANSWER:Fixed
Local currents ____. - ANSWER:Flactuate
Rip current - ANSWER:Current which goes seaward due to ocean floor stuctures
Long shore current - ANSWER:Flows parallel to shore
Waves are caused by - ANSWER:energy generated by WIND
, Tides are caused by - ANSWER:polarity of the moon
T/F: Anticipate surge action to avoid contact with stationary objects. - ANSWER:True
What is surge - ANSWER:Back and forth motion underwater which you shouldn't fight; move deeper and
away from dangerous objects if caught in one. USE THEM TO YOUR ADVANTAGE
What types of marine life cause most diving injuries - ANSWER:Jellyfish or marine life which account for
a temporary, painful sting. WATCH OUT FOR ALLERGIC REACTIONS.
Injuries due to marine life typically a _____ response - ANSWER:Defense
How do you treat a sting? - ANSWER:Hot water or vinegar
What should you do if a potentially dangerous animal underwater does not leave your area? -
ANSWER:Remain still
Remain calm
Slowly leave area
List three different reasons that it is advisable to check with your local dive center before diving in an
unfamiliar area. - ANSWER:1) Rip currents could be prevalent
2) Thermoclines could affect thermal protection
3) YOU ARE SUBJECT TO LOCALITY (be aware of laws and regulations
What is the absolute pressure in atm at 20m/66ft? - ANSWER:3 atm absolute
What will be the volume in a ball that is filled with 2 cubic feet of air at 30 m/99ft when it is taken to the
surface? - ANSWER:8 cubic feet
How many times more dense is air in a balloon at 4 atm compared to the air density at the surface? -
ANSWER:4 times
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? - ANSWER:40 min
How often should you equalize during descent? - ANSWER:Early and often; at the surface and then every
couple feet so no discomfort is felt
What should you do if you experience discomfort in your ears upon descending? - ANSWER:Immediately
stop descending and ascend a few feet until you are shallow enough not to feel any discomfort
What is reverse block? - ANSWER:Occurs when air cannot expand or escape freely when ascending
What should you do if you experience a reverse block upon ascending? - ANSWER:Descend a couple feet
and stay there until air has time to vent
What is the most important rule in scuba diving? - ANSWER:Do not hold your breath, breathe
continuously
What is the most serious injury that a diver could suffer from if they hold their breathe upon ascending?
- ANSWER:Lung overexpansion injuries
