Scuba Flashcards
Underwater objects appear how much closer?
25%
Underwater objects appear how much larger?
1/3
As you descend what colors disappear first?
Reds and oranges
How much denser is water than air?
800x denser
How much faster does sound move in water?
4x faster
Water conducts heat away from your body ____ times faster than air does?
25x faster
When should you wear thermal protection?
Always
Water stratifies into layers by temp. what is the name of the boundary?
Thermocline
What is the primary cause of waves?
Wind
What forms surf?
The bottom of the wave slows causing the wave to break
What is the back and forth movement of water caused by waves passing overhead called?
Surge
Tides can affect what three things?
Depth, current, visibility
What 2 things cause most permanent ocean currents?
- The sun warming ocean water at the equator
- The earth’s rotation
What direction do rip currents flow compared to shore?
Perpendicular to shore
Where should you swim to get out of a rip current?
Parallel to shore
How do we measure wave height?
From the crest to the trough
How do we measure wave length?
Crest to crest
Long shore currents can be created by what four things?
- Wind
- Tides
- Waves
- Nearby ocean currents
What direction does a long shore current run compared to shore?
Parallel to shore
Aquatic life injuries are most often a result of?
Diver carelesness
The most common aquatic life injuries are?
Scraps and abrasions
Most aquatic bites result from?
- Preserved threat
- Mistaken identity
Some animals posses stinging cells called?
Nematocysts
What should you do if you plan to dive in an unfamiliar environment?
Contact your local SDI center
What are the three states of buoyancy?
- Positive
- Negative
- Neutral
___ items float ___ items sink ___ items do neither?
- Positive
- Negative
- Neutral
How much does ambient pressure increase by for every 10 meters/33 feet of descent in sea water?
One atmospheric bar
What is the ambient pressure at sea level?
One
As you descend pressure ___ and volume ___?
Pressure increases
Volume decreases
What is the pressure at 30 meter under water?
4
At a depth of 20 meters how much more air will you use than you use at the surface?
4
How do you prevent an ear squeeze?
Equalize early and often
What is the #1 rule of scuba?
Don’t hold your breath
What is the #2 rule of scuba?
Equalize early and often
What medicine should you not take?
Decongestants
With what illness should you never dive with?
Anything that causes Decongestant
How do you prevent and tooth squeeze?
Regular dental care
How do you prevent a mask squeeze?
Exhale through your nose
When might you suffer a reverse block?
During acent
What should you do when you occur against a reverse block?
Go down and equalize
What does holding your breath put you at risk of?
Lung explosion
What causes an ear squeeze?
Pressure inside ear is less than surrounding pressure
What should you do if you cannot inhale while diving?
Continue exhaling
What should you do if you feel pain during descent?
Go up Equalize Decend
A scuba cylinder than normally last at the surface will last ___ minutes at 20 meters?
20 minutes
What should you do before descent?
Equalize
