SDI Scuba Certification Exam Study
Guide
What type of marine life cause most diving injuries? - ✔️✔️Most diving injuries result
from animal's defensive response to a perceived threat
How much larger and closer do objects appear underwater and why? - ✔️✔️Objects
underwater appear 25% larger and 25% closer
What sets SDI apart from other training agencies? - ✔️✔️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
Define SCUBA - ✔️✔️S - self
C - contained
U - underwater
B - breathing
A - apparatus
List 3 important scuba diving changes that occurred in 1950s - ✔️✔️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 - ✔️✔️1) dive tables
2) J-valves
3) depth gauges
water
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? - ✔️✔️4 times
faster because water is about 800 times denser than air.
What is the first color to be absorbed underwater? - ✔️✔️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. - ✔️✔️Slack tide
If you are caught in a rip current, first swim _____ to the current to get out of it before
swimming towards shore. - ✔️✔️Parallel
, Waves are usually caused by - ✔️✔️Wind pushing water on the surface
T or F: Anticipate surge action to avoid contact with stationary objects - ✔️✔️True
What should you do if you see a potentially dangerous animal underwater and it does
not leave the area? - ✔️✔️Remain still and calm. Slowly leave area if necessary.
What is the absolute pressure (in atm/bar) at 20 meters (66 feet)? - ✔️✔️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? - ✔️✔️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? - ✔️✔️4x
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? -
✔️✔️40 minutes
120 min x 1/3 (vol) = 40 min
How often should a scuba diver equalize during descent? - ✔️✔️At the surface before
descent and every couple of feet
What should you do if you experience discomfort in your ears upon descending? -
✔️✔️Stop, ascend a few feet until you no longer feel discomfort, equalize again, then
continue with descent
What is a reverse block? - ✔️✔️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? - ✔️✔️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? - ✔️✔️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? - ✔️✔️Lung over-expansion
Guide
What type of marine life cause most diving injuries? - ✔️✔️Most diving injuries result
from animal's defensive response to a perceived threat
How much larger and closer do objects appear underwater and why? - ✔️✔️Objects
underwater appear 25% larger and 25% closer
What sets SDI apart from other training agencies? - ✔️✔️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
Define SCUBA - ✔️✔️S - self
C - contained
U - underwater
B - breathing
A - apparatus
List 3 important scuba diving changes that occurred in 1950s - ✔️✔️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 - ✔️✔️1) dive tables
2) J-valves
3) depth gauges
water
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? - ✔️✔️4 times
faster because water is about 800 times denser than air.
What is the first color to be absorbed underwater? - ✔️✔️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. - ✔️✔️Slack tide
If you are caught in a rip current, first swim _____ to the current to get out of it before
swimming towards shore. - ✔️✔️Parallel
, Waves are usually caused by - ✔️✔️Wind pushing water on the surface
T or F: Anticipate surge action to avoid contact with stationary objects - ✔️✔️True
What should you do if you see a potentially dangerous animal underwater and it does
not leave the area? - ✔️✔️Remain still and calm. Slowly leave area if necessary.
What is the absolute pressure (in atm/bar) at 20 meters (66 feet)? - ✔️✔️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? - ✔️✔️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? - ✔️✔️4x
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 m/66 ft? -
✔️✔️40 minutes
120 min x 1/3 (vol) = 40 min
How often should a scuba diver equalize during descent? - ✔️✔️At the surface before
descent and every couple of feet
What should you do if you experience discomfort in your ears upon descending? -
✔️✔️Stop, ascend a few feet until you no longer feel discomfort, equalize again, then
continue with descent
What is a reverse block? - ✔️✔️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? - ✔️✔️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? - ✔️✔️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? - ✔️✔️Lung over-expansion
