SDI FINAL EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS
n Objects under water appear:
1: The same size as they do on land.
2: Twice as large as they do on land.
3: Closer and larger than they do on land.
4: Smaller and farther away than they do on land. - Closer and larger than they do on land.
As you descend:
1: Colors appear to fade.
2: Reds and oranges are among the first colors to disappear.
3: At 30 m/99 ft, little color remains other than blues, grays, blacks and whites.
4: All of the above. - All of the above.
Which of the following statements is true? There may be more than one correct answer.
1: Water is 400 times denser than air.
2: Water is 800 times denser than air.
3: Sound travels about four times faster underwater.
4: Both the second and the third answer are correct. - Both the second and the third answer are correct.
Which of the following is/are true?
1: Water conducts heat away from your body ten times faster than air does.
2: Water conducts heat away from your body 25 times faster than air does.
3: Fresh water conducts heat away from your body faster than salt water does.
4: Salt water conducts heat away from your body faster than fresh water does. - Water conducts heat
away from your body 25 times faster than air does.
When water stratifies itself into layers, according to temperature, the boundary between layers is known
as a(n):
1: Halocline.
2: Ichtyocline.
,3: Thermodyne.
4: Thermocline. - Thermocline.
Which of the following is/are true?
1: Tides can make the water at a particular dive site noticeably deeper or shallower than you may have
experienced previously.
2: Tidal currents can be very strong, making diving difficult or even dangerous.
3: Strong tidal currents can have an adverse effect on visibility.
4: All of the above. - All of the above.
The sun warming water near the equator, coupled with the earth's rotation, is the primary cause of
permanent ocean currents.
1: True.
2: False. - True.
Which of the following is/are true?
1: If caught in a rip current, swim directly towards shore, using the most powerful kick possible.
2: If caught in a rip current, swim perpendicular to shore, until you are completely out of the rip current,
then swim in towards shore.
3: If caught in a rip current, swim parallel to shore, until you are completely out of the rip current, then
swim in towards shore.
4: Don't fight the rip current; relax and let it carry you closer to shore. - If caught in a rip current, swim
parallel to shore, until you are completely out of the rip current, then swim in towards shore.
We measure waves by their height and weight.
1: True.
2: False. - False.
Explanation:
We measure waves by their height and length.
Which of the following best describes the formation of surf?
1: Waves energy, rebounding from its impact with shore, crashes into oncoming waves, causing them to
break.
2: Entering shallow water forces wave energy upward, making the wave crest unstable and causing it to
break.
, 3: A wave encountering shallow water begins to slow at its bottom, while the top of the wave continues
at its previous speed. This causes the wave to break.
4: As waves enter shallow water, the distance between wave crests (wave length) shortens, increasing
the tendency to break. - Only the third answer (A wave encountering shallow water begins to slow at it
bottom, while the top of the wave continues at its previous speed; this causes the wave to break) is
correct.
Surge:
1: Occurs when waves force water between facing rock ledges.
2: Is the back-and-forth movement of water caused by waves passing over head.
3: Is the backwash of water from waves breaking on shore.
4: None of the above. - Surge is the back-and-forth movement of water caused by waves passing over
head.
Which 'if any' of the following are true?
1: Aquatic animals present a greater risk to divers than any other factor.
2: Most aquatic animal bites result from an animal's defensive response to a perceived threat or, on rare
occasions, from a case of mistaken identify.
3: Because they are perceived as more aggressive, men are more likely to be the victim of an aquatic
animal attack than women are.
4: None of the above. - Most aquatic animal bites result from an animal's defensive response to a
perceived threat or, on rare occasions, from a case of mistaken identify.
Psoriacysts produce toxins that, when touched, can produce symptoms ranging from a mild rash or sting
to anaphylactic shock or even paralysis.
1: True.
2: False. - False.
Explanation:
Nematocysts produce toxins that, when touched, can produce symptoms ranging from a mild rash or
sting to anaphylactic shock or even paralysis.
Depending on circumstances, there are times when divers may wish to be positively, negatively or
neutrally buoyant.
1: True.
2: False. - True.
CORRECT DETAILED ANSWERS
n Objects under water appear:
1: The same size as they do on land.
2: Twice as large as they do on land.
3: Closer and larger than they do on land.
4: Smaller and farther away than they do on land. - Closer and larger than they do on land.
As you descend:
1: Colors appear to fade.
2: Reds and oranges are among the first colors to disappear.
3: At 30 m/99 ft, little color remains other than blues, grays, blacks and whites.
4: All of the above. - All of the above.
Which of the following statements is true? There may be more than one correct answer.
1: Water is 400 times denser than air.
2: Water is 800 times denser than air.
3: Sound travels about four times faster underwater.
4: Both the second and the third answer are correct. - Both the second and the third answer are correct.
Which of the following is/are true?
1: Water conducts heat away from your body ten times faster than air does.
2: Water conducts heat away from your body 25 times faster than air does.
3: Fresh water conducts heat away from your body faster than salt water does.
4: Salt water conducts heat away from your body faster than fresh water does. - Water conducts heat
away from your body 25 times faster than air does.
When water stratifies itself into layers, according to temperature, the boundary between layers is known
as a(n):
1: Halocline.
2: Ichtyocline.
,3: Thermodyne.
4: Thermocline. - Thermocline.
Which of the following is/are true?
1: Tides can make the water at a particular dive site noticeably deeper or shallower than you may have
experienced previously.
2: Tidal currents can be very strong, making diving difficult or even dangerous.
3: Strong tidal currents can have an adverse effect on visibility.
4: All of the above. - All of the above.
The sun warming water near the equator, coupled with the earth's rotation, is the primary cause of
permanent ocean currents.
1: True.
2: False. - True.
Which of the following is/are true?
1: If caught in a rip current, swim directly towards shore, using the most powerful kick possible.
2: If caught in a rip current, swim perpendicular to shore, until you are completely out of the rip current,
then swim in towards shore.
3: If caught in a rip current, swim parallel to shore, until you are completely out of the rip current, then
swim in towards shore.
4: Don't fight the rip current; relax and let it carry you closer to shore. - If caught in a rip current, swim
parallel to shore, until you are completely out of the rip current, then swim in towards shore.
We measure waves by their height and weight.
1: True.
2: False. - False.
Explanation:
We measure waves by their height and length.
Which of the following best describes the formation of surf?
1: Waves energy, rebounding from its impact with shore, crashes into oncoming waves, causing them to
break.
2: Entering shallow water forces wave energy upward, making the wave crest unstable and causing it to
break.
, 3: A wave encountering shallow water begins to slow at its bottom, while the top of the wave continues
at its previous speed. This causes the wave to break.
4: As waves enter shallow water, the distance between wave crests (wave length) shortens, increasing
the tendency to break. - Only the third answer (A wave encountering shallow water begins to slow at it
bottom, while the top of the wave continues at its previous speed; this causes the wave to break) is
correct.
Surge:
1: Occurs when waves force water between facing rock ledges.
2: Is the back-and-forth movement of water caused by waves passing over head.
3: Is the backwash of water from waves breaking on shore.
4: None of the above. - Surge is the back-and-forth movement of water caused by waves passing over
head.
Which 'if any' of the following are true?
1: Aquatic animals present a greater risk to divers than any other factor.
2: Most aquatic animal bites result from an animal's defensive response to a perceived threat or, on rare
occasions, from a case of mistaken identify.
3: Because they are perceived as more aggressive, men are more likely to be the victim of an aquatic
animal attack than women are.
4: None of the above. - Most aquatic animal bites result from an animal's defensive response to a
perceived threat or, on rare occasions, from a case of mistaken identify.
Psoriacysts produce toxins that, when touched, can produce symptoms ranging from a mild rash or sting
to anaphylactic shock or even paralysis.
1: True.
2: False. - False.
Explanation:
Nematocysts produce toxins that, when touched, can produce symptoms ranging from a mild rash or
sting to anaphylactic shock or even paralysis.
Depending on circumstances, there are times when divers may wish to be positively, negatively or
neutrally buoyant.
1: True.
2: False. - True.
