Scuba AFS 270 SDI Midterm Exam Questions and
Answers.
Closer and larger - answer objects underwater appear ___ and then they do on land
4 (none of the above) - answer as you descend:
1: Colors will remain largely the same.
2: Blues and grays disappear quickly.
3: Dive lights have little effect on apparent color.
4: None of the above.
25x - answer Water conducts heat away from your body ____x as fast as air does
Thermocline - answer when water stratifies itself into layers, according to temperature,
the boundary between layers is known as a (n):
4 (all of the above) - answer 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.
2 (Water conducts heat away from your body 25 times faster than air does) - answer
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.
3 (Divers may require more in the way of exposure protection at depth than they will at
the surface) - answer the presence of thermoclines means that:
1: Surface temperatures will provide divers with a good indication of what they can
expect at depth.
2: Divers may require less in the way of exposure protection at depth than they will at
the surface.
3: Divers may require more in the way of exposure protection at depth than they will at
the surface.
4: None of the above.
4 (both the first and second answers are correct) - answer which of the following
statements are true?
1: Wave height is the distance from its highest point (crest) to its lowest point (trough).
2: Wave length is the distance from crest to crest.
3: Wave oscillation to calculate by multiplying the wave height times its length.
,4: Both the first and second answers are correct.
TRUE - answer TRUE OR FALSE: In general, the best time to dive is during slack tide,
the period between high and low tides.
True - answer TRUE OR FALSE: The sun warming water near the equator, coupled
with the earth's rotation, is the primary cause of permanent ocean currents.
True - answer T/F
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.
All of the above - answer which of the following statements is/are true?
1: A rip current is a narrow flow of swiftly moving water that runs perpendicular to shore.
2: Rip currents form when water flowing out to sea is funneled through a narrow
restriction, such as two sandbars or a break in a coral reef.
3: The force of a rip current generally diminishes in deeper water, not far beyond the
surf zone.
4: All of the above.
2 (Surge is the back-and-forth movement of water caused by waves passing over
head.) - answer which of the following is/are true?
1: Surge is the backwash of water from waves breaking on shore.
2: Surge is the back-and-forth movement of water caused by waves passing over head.
3: Surge occurs when waves force water between facing rock ledges.
4: None of the above.
(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. - answer 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.
True (aquatic life injuries) - answer T/F
Most aquatic life injuries amount to no more than a temporary, yet painful, sting or
abrasion.
False (it's actually nematocysts) - answer T/F
Psoriacysts produce toxins that, when touched, can produce symptoms ranging from a
mild rash or sting to anaphylactic shock or even paralysis.
, 2: Nematocysts. - answer some aquatic animals possess stinging cells. These cells are
called:
1: Hypothocysts.
2: Nematocysts.
3: Psoriacysts.
4: None of the above.
true (buoyant) - answer T/F
Depending on circumstances, there are times when divers may wish to be positively,
negatively or neutrally buoyant.
20 minutes - answer a scuba cylinder that normally lasts one hour at the surface will last
_______ minutes at 20 meters/66 feet.
3 (as soon as they feel any pain or discomfort) - answer which of the following is not
true? Divers should equalize:
1: Preemptively before descent.
2: Well before feeling any pain or discomfort.
3: As soon as they feel any pain or discomfort.
4: Early and often during descent.
False (squeeze) - answer T/F
Taking decongestants is a good way to reduce the risk of ear or sinus squeeze.
(1) You can help prevent mask squeeze by exhaling periodically into your mask during
ascent. - Answer all of the following are true accept:
1: You can help prevent mask squeeze by exhaling periodically into your mask during
ascent.
2: Regular dental care and ensuring your teeth are free of gas spaces can help prevent
tooth squeeze.
3: If you experience a reverse block, descend to a point where the pain subsides, then
ascend slowly while wiggling your jaw and swallowing. Repeat this process as needed
until you can ascend without pain or discomfort.
4: The danger in taking decongestants is that they may wear off during a dive and have
other possible side effects.
(2) Ascend to the point where you can comfortably equalize, and only then continue
your descent. - answer if you feel pain or discomfort during descent:
1: Stop, hold in place and equalize forcefully until your ears clear.
2: Ascend to the point where you can comfortably equalize, and only then continue your
descent.
3: Abort the dive and consult a physician.
4: Note the depth at which the pain occurred and conduct your safety stop there at the
end of the dive.
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