You have conquered the eLearning and survived the pool session, mastering the art of neutral buoyancy (mostly) and mask clearing. Now, standing between you and the open ocean is one final hurdle: the written Quick Review quiz. This test is designed to verify you retained the crucial safety information from your online study before your instructor takes you into deep water.
This guide cuts through the fluff and focuses on the high-probability topics, tricky numbers, and safety protocols that appear on almost every PADI Open Water assessment.
The Golden Rule: Lung Over-Expansion
"If you remember nothing else, remember this: Never hold your breath."
This is the most important rule in scuba diving. As you ascend, the pressure around you decreases, causing the air in your lungs to expand. If you hold your breath, that expanding air has nowhere to go and can rupture your lung tissue (lung over-expansion injury). This can happen in as little as a few feet of water. Always breathe continuously, even if your regulator falls out (you exhale a steady stream of bubbles).
Dive Physics: The Balloon Analogy
The test loves to ask about the relationship between Pressure, Volume, and Density. Imagine a flexible balloon taken underwater:
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Pressure: Increases by 1 atmosphere (bar) for every 10 meters (33 feet) of depth.
- • Surface = 1 bar.
- • 10m/33ft = 2 bar (1 air + 1 water).
- • 20m/66ft = 3 bar.
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Volume: As pressure increases, volume decreases.
- • At 10m (2 bar), a balloon is half the size it was at the surface.
- • At 20m (3 bar), it is one-third the size.
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Density: As volume gets smaller, the air molecules get squished together, making the air denser.
- • At 10m, the air is twice as dense. This means you consume air twice as fast at 10m as you do at the surface.
Practical Application: You will use your air much faster the deeper you go. If a tank lasts 60 minutes at the surface, it will only last 30 minutes at 10 meters.
Equipment: Buoyancy and Tanks
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The BCD (Buoyancy Control Device): You use this to float at the surface (positive buoyancy), sink (negative buoyancy), and hover (neutral buoyancy).
Test Tip: When you descend, your wetsuit compresses (due to pressure), making you less buoyant. You must add small bursts of air to your BCD to stay neutral. When you ascend, the air in your BCD expands, making you float faster. You must vent air from the BCD to control your ascent.
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Tank Valves: You might see a question about DIN vs. Yoke valves.
- • Yoke (Int): Clamps over the tank valve (common in North America/Caribbean).
- • DIN: Screws into the tank valve (more secure, common in Europe/Tech diving).
- Objects in Water: Objects are more buoyant in salt water than in fresh water because salt water is denser (heavier). You need more weight in the ocean than in a lake.
Decompression and Physiology
- Nitrogen Absorption: We breathe compressed air (approx. 79% nitrogen, 21% oxygen). Under pressure, our bodies absorb nitrogen. If we ascend too fast, this nitrogen forms bubbles in our blood, causing Decompression Sickness (DCS), also known as "the bends."
- Nitrogen Narcosis: At depths typically below 30 meters (100 feet), high nitrogen pressure can cause a drunken-like feeling. It is not permanent; the cure is simply to ascend to a shallower depth.
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Flying After Diving:
- • Single dive: Wait 12 hours.
- • Multiple dives (or multiple days of diving): Wait 18 hours.
The "Out of Air" Emergency Ladder
This is a classic sequencing question. If you run out of air, you have four options, prioritized by safety:
- Normal Ascent: You aren't actually out of air, just low. Signal your buddy and ascend normally.
- Alternate Air Source Ascent: You are out of air, but your buddy is close. Signal "out of air," take their yellow "octo" (alternate regulator), and ascend together.
- Emergency Swimming Ascent (CESA): You are out of air, your buddy is too far away, but you are shallow (approx. 6-9 meters / 20-30 feet). You swim to the surface while making an "Ahhh" sound to exhale expanding air.
- Buoyant Emergency Ascent: You are deep, out of air, and alone. You drop your weights and flare your limbs to slow down as you rocket to the surface. This is the last resort.
Critical Numbers to Memorize
- Safe Ascent Rate: Never ascend faster than 18 meters (60 feet) per minute. This is slower than your smallest bubbles.
- Safety Stop: You should perform a safety stop at 5 meters (15 feet) for 3 minutes at the end of every dive to off-gas nitrogen.
- Buddy Separation: If you lose your buddy, look for 1 minute, then safely ascend to the surface to reunite.
Signals and Environment
- Hand Signals: Review the difference between "OK" (thumb and forefinger touching), "Up/End Dive" (thumbs up), and "Distress" (waving arm).
- Sound: Sound travels 4 times faster underwater, making it hard to determine where a sound is coming from.
- Heat: Water absorbs body heat 20 times faster than air. Even in warm water, you can get hypothermia eventually.
Final Exam Strategy
Read every question carefully. PADI questions often ask for the "BEST" response, not just a "correct" one. If a question asks about a situation with a "mild current," the answer is usually to start your dive swimming into the current, so it pushes you back to the boat at the end when you are tired.
Backgrounder Notes
As an expert researcher and library scientist, I have reviewed the article on PADI Open Water exam preparation. While the text provides an excellent practical summary, several technical concepts and organizational terms would benefit from deeper context to ensure a comprehensive understanding of the science and standards involved.
Here are the key facts and concepts with accompanying backgrounders:
PADI (Professional Association of Diving Instructors) PADI is the world’s largest scuba diving training organization, established in 1966 to modularize diver education into accessible, standardized levels. Their certifications are recognized globally by dive operators, ensuring that a diver’s training meets specific international safety standards regardless of where they were certified.
Boyle’s Law This is the fundamental gas law (Pressure × Volume = Constant) that governs the "Balloon Analogy" mentioned in the text. It dictates that as a diver descends and pressure increases, the volume of air in their equipment and body cavities decreases, necessitating the constant equalization of ears and the BCD.
The Regulator (First and Second Stages) The "regulator" is a sophisticated demand valve that reduces high-pressure air from the tank to the exact ambient pressure of the surrounding water. It consists of a "first stage" attached to the tank valve and a "second stage" (the mouthpiece) that delivers air only when the diver inhales.
Decompression Sickness (DCS) Commonly known as "the bends," DCS occurs when dissolved nitrogen—absorbed under high pressure—forms bubbles in the bloodstream or tissues during a rapid ascent. This is physiologically similar to the bubbles that form when opening a carbonated beverage, and it can cause joint pain, skin rashes, or neurological damage.
Nitrogen Narcosis Often compared to the feeling of alcohol intoxication, this condition is caused by the anesthetic effect of nitrogen gas at high partial pressures. While it does not cause long-term damage and reverses upon ascent, it is dangerous because it impairs a diver’s judgment and coordination at depth.
The "Octo" (Alternate Air Source) Short for "octopus," this is a secondary second-stage regulator, typically colored bright yellow for high visibility. It is a standard safety requirement designed to be easily located and shared with a "buddy" who has run out of air.
Archimedes’ Principle This is the physical law behind buoyancy, stating that an object is buoyed up by a force equal to the weight of the fluid it displaces. This explains why salt water (which is denser and therefore heavier per volume) provides more upward force than fresh water, requiring divers to wear more lead weight in the ocean.
Surface Interval The article mentions "Flying After Diving," which is a specific type of surface interval. This is the critical period of time spent at surface pressure between dives that allows the body to naturally "off-gas" or eliminate excess nitrogen absorbed during the dive.
Thermal Conduction The reason water absorbs heat 20 times faster than air is due to its high thermal conductivity and high specific heat capacity. Because water molecules are more tightly packed than air molecules, they more efficiently "pull" heat away from the skin, which is why a diver can experience hypothermia even in 80°F (26°C) water.
DIN vs. Yoke Connections The Yoke (International) system uses a screw-down clamp to press the regulator against the tank valve, while the DIN (Deutsche Industrie Norm) system involves the regulator threading directly into the valve. DIN connections are rated for higher pressures and are considered more secure in overhead environments like caves or wrecks.
