PADI Open Water Dive Manual Review

Flashcards covering PADI Open Water Diver theory, including pressure physics, buoyancy, equipment, safety procedures, and decompression theory based on the dive manual review.

Surface Pressure

The amount of air pressure surrounding us at sea level, which is equal to $1 ext{ bar}$ or one atmosphere.

Pressure Increase with Depth

The rate at which water pressure increases as a diver descends, calculated at an increase of $1 ext{ bar}$ for every $10 ext{ meters}$ of depth.

Atmospheres (Total Pressure)

The sum of air pressure at the surface and water pressure at depth; for example, at $10 ext{ meters}$ the total pressure is $2 ext{ bar}$ ($1 ext{ bar}$ air + $1 ext{ bar}$ water).

Bouncy-Volume Relationship

As pressure increases, the volume of a flexible air space (like a balloon) decreases proportionally; at $10 ext{ meters}$ ($2 ext{ bar}$), the volume is halved ($1/2$).

Bouncy-Density Relationship

As pressure increases and volume decreases, the density of gas molecules increases; at $10 ext{ meters}$ ($2 ext{ bar}$), the density of the air is twice ($2 imes$) its surface density.

Equalization

The process of adding air to body air spaces, such as the ears and sinuses, to balance internal and external pressure during descent.

Valsalva Maneuver

An equalization technique where a diver gently pinches their nose and blows against a closed mouth and nose to force air into the eustachian tubes.

Squeeze

An uncomfortable or painful condition caused by a pressure imbalance where external pressure is greater than the internal pressure within an air space.

Maximum Depth (Open Water Diver)

The final depth limit allowed for PADI Open Water Divers, which is $18 ext{ meters}$ ($60 ext{ feet}$).

Most Important Rule of Scuba Diving

Never hold your breath and always breathe continuously to ensure lungs are equalized and to prevent lung overexpansion injuries.

Reverse Block

A condition occurring during ascent when expanding air becomes trapped in an air space (like sinuses or ears), typically caused by congestion or medication wearing off.

Air Consumption and Depth

The rate at which a diver uses their air supply increases with depth; at $30 ext{ meters}$ ($4 ext{ bar}$), a diver uses air four times ($4 imes$) faster than at the surface.

Overexertion

A condition caused by excessive physical activity underwater, leading to high levels of carbon dioxide ($CO_2$), shallow breathing, and potential panic.

Neutral Buoyancy

The state when an object displaces an amount of water equal to its own weight, allowing it to remain suspended without sinking or floating.

Saltwater vs. Freshwater Buoyancy

Objects float more easily in saltwater because it is denser and heavier than freshwater due to its salt content.

Buddy System

A safety practice where divers dive together to provide assistance, improve practicality, and enhance the fun of the experience.

Inspection Requirement

The recommendation that scuba equipment should be professionally inspected and serviced at least once a year.

DIN and Yoke

The two primary types of regulator-to-cylinder valve connections; DIN is a screw-in system, while Yoke is a clamp-on pressure connection.

Refraction

An underwater visual effect that makes objects appear approximately $33 ext{ imes}$ larger and closer than they actually are.

Color Absorption

The phenomenon where water absorbs light wavelengths as depth increases, with red being the first color to disappear and turn brownish.

Trim

The horizontal, streamlined position a diver maintains to move through the dense medium of water with maximum efficiency.

Thermal Loss in Water

Water conducts heat away from the body approximately $20 ext{ times}$ faster than air does.

Lost Buddy Procedure

If separated, divers should search for no more than one minute, then slowly surface and reunite at the surface.

Five Point Descent (SORTED)

A structured descent procedure consisting of: Signal, Orientation, Regulator/Snorkel switch, Time check, and Equalize/Descend.

Neoprene

The material used in wetsuits that provides insulation but compresses under pressure, resulting in loss of buoyancy at depth.

Maximum Ascent Rate

The safe speed limit for returning to the surface, which must not exceed $18 ext{ meters/minute}$ ($60 ext{ feet/minute}$).

Safety Stop

A precautionary stop made at $5 ext{ meters}$ for $3 ext{ minutes}$ at the end of every dive to reduce the risk of decompression sickness.

Exposure Suits

Protective clothing for divers, including rash guards (skin protection), wetsuits (insulation), and drysuits (keeping the diver completely dry).

Local Orientation

A briefing on specific conditions, hazards, and interests of a new dive site provided by a local professional.

Nitrogen Absorption

The process where the body absorbs nitrogen ($N_2$) from compressed air during a dive due to increased ambient pressure.

No Decompression Limit (NDL)

The maximum amount of time a diver can stay at a specific depth and still perform a direct ascent to the surface without a mandatory decompression stop.

Decompression Sickness (DCS)

An injury caused by nitrogen bubbles forming in body tissues or blood when a diver stays too long underwater or ascends too quickly.

Signs of DCS

Symptoms including joint pain, numbness, tingling ("needles"), skin rash, and extreme fatigue.

Gas Narcosis (Nitrogen Narcosis)

An intoxicating effect on the nervous system caused by nitrogen under high pressure at depth, resulting in euphoria, anxiety, or slowed reactions.

Recompression Chamber

A medical device used to treat decompression sickness by placing the diver under pressure to force nitrogen bubbles back into solution.

Enriched Air (Nitrox)

Gas with a lower nitrogen ($N_2$) content and higher oxygen ($O_2$) content (above $21 ext{ imes}$) used to extend no-stop dive times.

Oxygen Toxicity

A dangerous condition caused by breathing high partial pressures of oxygen at depth, which can lead to convulsions or drowning.

Flying After Diving

The recommendation to wait at least $12 ext{ hours}$ after a single dive and $18 ext{ hours}$ after multiple dives before boarding an airplane.

Compass Components

Tools for underwater navigation including the bezel (rotating ring), index marks, and the lubber line (direction of travel).

Controlled Emergency Swimming Ascent (CESA)

An out-of-air emergency procedure where a diver swims to the surface while continuously exhaling an "ah" sound to prevent lung injury.