Study Guide: SDI Scuba Certification Exam Study Guide:
Questions & Answers
Define SCUBA - ANSWER:S - self
C - contained
U - underwater
B - breathing
A - apparatus
List 3 important scuba diving changes that occurred in 1950s - ANSWER:1) published USN dive tables
2) invented the personal dive computer
3) equipment manufacturers made improvements to the design and workmanship of gear
Name 3 different devices that modern dive computers replace - ANSWER:1) dive tables
2) J-valves
3) depth gauges
What sets SDI apart from other training agencies? - ANSWER:First dive training agency to provide entry
level scuba instruction that incorporates the use of personal dive computers --> more streamlined scuba
course w/ more instruction time in the water
How much larger and closer do objects appear underwater and why? - ANSWER:Objects underwater
appear 25% larger and 25% closer
As light travels through the airspace created by the mask, it bends, creating a magnifying effect.
How much faster does sound move through water than air and why? - ANSWER:4 times faster because
water is about 800 times denser than air.
What is the first color to be absorbed underwater? - ANSWER:Red (within first 25 feet)
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 tide
If you are caught in a rip current, first swim _____ to the current to get out of it before swimming
towards shore. - ANSWER:Parallel
Waves are usually caused by - ANSWER:Wind pushing water on the surface
T or F: Anticipate surge action to avoid contact with stationary objects - ANSWER:True
, What type of marine life cause most diving injuries? - ANSWER:Most diving injuries result from animal's
defensive response to a perceived threat
What should you do if you see a potentially dangerous animal underwater and it does not leave the
area? - ANSWER:Remain still and calm. Slowly leave area if necessary.
List three different reasons that it is advisable to check with your local dive center before conducting a
dive in an area you are unfamiliar with? - ANSWER:1) tidal conditions
2) marine life
3) first aid for potential injuries in area
What is the absolute pressure (in atm/bar) at 20 meters (66 feet)? - ANSWER:3 atm/bar
What will be the volume in a ball that is filled with 2 cubic feet/liters of air at 30 meters (90 feet) when it
is taken to surface? - ANSWER:8 cubic feet/liter (4x the volume)
How many more times dense is the air in a ballon at 4 atm/bar compared to air density at surface? -
ANSWER:4x
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? - ANSWER:40 minutes
120 min x 1/3 (vol) = 40 min
How often should a scuba diver equalize during descent? - ANSWER:At the surface before descent and
every couple of feet
What should you do if you experience discomfort in your ears upon descending? - ANSWER:Stop, ascend
a few feet until you no longer feel discomfort, equalize again, then continue with descent
What is a reverse block? - ANSWER:When air cannot escape freely from an air space during ascent
causes pain and discomfort in the ears and sinuses
What should you do if you experience a reverse block upon ascending? - ANSWER:Stop, descend a few
feet until pain subsides, wait to allow air to vent, then continue with ascent
What is the most important rule in scuba diving? - ANSWER:Breathe continuously and never hold your
breath
What is the most serious injury that a diver could suffer from if they hold their breath upon ascending? -
ANSWER:Lung over-expansion
Which gas component in air causes decompression sickness and narcosis? - ANSWER:Nitrogen
What medical problem can occur if a diver ascends much too rapidly for nitrogen to be slowly released? -
ANSWER:Decompression sickness
Questions & Answers
Define SCUBA - ANSWER:S - self
C - contained
U - underwater
B - breathing
A - apparatus
List 3 important scuba diving changes that occurred in 1950s - ANSWER:1) published USN dive tables
2) invented the personal dive computer
3) equipment manufacturers made improvements to the design and workmanship of gear
Name 3 different devices that modern dive computers replace - ANSWER:1) dive tables
2) J-valves
3) depth gauges
What sets SDI apart from other training agencies? - ANSWER:First dive training agency to provide entry
level scuba instruction that incorporates the use of personal dive computers --> more streamlined scuba
course w/ more instruction time in the water
How much larger and closer do objects appear underwater and why? - ANSWER:Objects underwater
appear 25% larger and 25% closer
As light travels through the airspace created by the mask, it bends, creating a magnifying effect.
How much faster does sound move through water than air and why? - ANSWER:4 times faster because
water is about 800 times denser than air.
What is the first color to be absorbed underwater? - ANSWER:Red (within first 25 feet)
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 tide
If you are caught in a rip current, first swim _____ to the current to get out of it before swimming
towards shore. - ANSWER:Parallel
Waves are usually caused by - ANSWER:Wind pushing water on the surface
T or F: Anticipate surge action to avoid contact with stationary objects - ANSWER:True
, What type of marine life cause most diving injuries? - ANSWER:Most diving injuries result from animal's
defensive response to a perceived threat
What should you do if you see a potentially dangerous animal underwater and it does not leave the
area? - ANSWER:Remain still and calm. Slowly leave area if necessary.
List three different reasons that it is advisable to check with your local dive center before conducting a
dive in an area you are unfamiliar with? - ANSWER:1) tidal conditions
2) marine life
3) first aid for potential injuries in area
What is the absolute pressure (in atm/bar) at 20 meters (66 feet)? - ANSWER:3 atm/bar
What will be the volume in a ball that is filled with 2 cubic feet/liters of air at 30 meters (90 feet) when it
is taken to surface? - ANSWER:8 cubic feet/liter (4x the volume)
How many more times dense is the air in a ballon at 4 atm/bar compared to air density at surface? -
ANSWER:4x
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? - ANSWER:40 minutes
120 min x 1/3 (vol) = 40 min
How often should a scuba diver equalize during descent? - ANSWER:At the surface before descent and
every couple of feet
What should you do if you experience discomfort in your ears upon descending? - ANSWER:Stop, ascend
a few feet until you no longer feel discomfort, equalize again, then continue with descent
What is a reverse block? - ANSWER:When air cannot escape freely from an air space during ascent
causes pain and discomfort in the ears and sinuses
What should you do if you experience a reverse block upon ascending? - ANSWER:Stop, descend a few
feet until pain subsides, wait to allow air to vent, then continue with ascent
What is the most important rule in scuba diving? - ANSWER:Breathe continuously and never hold your
breath
What is the most serious injury that a diver could suffer from if they hold their breath upon ascending? -
ANSWER:Lung over-expansion
Which gas component in air causes decompression sickness and narcosis? - ANSWER:Nitrogen
What medical problem can occur if a diver ascends much too rapidly for nitrogen to be slowly released? -
ANSWER:Decompression sickness
