Air Consumption Rate (ACR) measures the volume of breathing gas a diver consumes per minute under specific conditions, usually surface pressure.
A Backplate and Wing (BPW) is a modular buoyancy system composed of a metal backplate and an inflatable air bladder worn on a diver’s back.
Barotrauma is a pressure-related injury caused when internal air spaces in the body cannot equalize with the surrounding water pressure during a dive.
A BCD is an inflatable jacket or harness that allows divers to control their buoyancy underwater and maintain positive buoyancy on the surface.
Bottom time is the total time a diver spends at depth during a dive, from the beginning of descent to the start of the final ascent.
Breathing gas is a specially blended mixture of gases used by divers to breathe underwater at various depths.
A buddy check is a pre-dive safety procedure where dive partners inspect each other’s gear to ensure functionality and preparedness.
Cavern diving is a form of overhead environment diving where divers remain within sight of natural light and maintain direct access to the surface.
In scuba diving, a decompression ceiling is the shallowest depth a diver can safely ascend to without exceeding tissue saturation limits.
Cold water diving refers to scuba diving in water temperatures typically below 15°C (59°F), which requires additional thermal protection and special equipment.
A scuba cylinder is a high-pressure tank used to store compressed breathing gas for underwater use.
Divers Alert Network (DAN) is a nonprofit organization dedicated to diver safety, emergency assistance, and dive medicine research.
A deco stop is a required pause at a specific depth during ascent to allow safe elimination of inert gases from a diver’s body.
Decompression sickness is a potentially serious condition caused by nitrogen bubbles forming in tissues during or after a rapid ascent.
A DIN valve is a type of scuba tank valve that allows the regulator to screw into the valve, offering a secure seal ideal for high-pressure diving.
A dive computer is a digital device that tracks a diver’s depth, time, and nitrogen absorption in real time to calculate a safe ascent profile.
A dive flag is a warning signal displayed at the surface to indicate that divers are underwater in the vicinity.
A Dive Master is a professional-level scuba certification that qualifies divers to supervise and assist in training other divers.
A dive table is a printed chart used to plan dives by estimating no-decompression limits and surface intervals based on depth and time.
A dry suit is an exposure suit that keeps the diver dry by sealing out water and providing thermal insulation with undergarments.
EANx, or Enriched Air Nitrox, is a breathing gas mixture with more oxygen and less nitrogen than standard air.
An emergency ascent is an unplanned return to the surface due to out-of-air situations, equipment failure, or diver distress.
Equalization is the act of balancing pressure in air spaces within the body with surrounding water pressure during descent.
The first stage regulator attaches to the scuba tank and reduces high-pressure air to an intermediate pressure for delivery to the second stage.
Free flow is a malfunction where a regulator continuously releases air, either due to freezing, mechanical failure, or improper handling.
The frog kick is a propulsion technique in scuba diving where the legs move outward and inward like a frog’s swimming motion.
The giant stride entry is a common method for entering the water from a boat or dock by stepping forward with one leg extended.
Hovering is the skill of maintaining neutral buoyancy at a fixed depth without ascending or descending.
A hydrostatic test is a pressure test performed on scuba cylinders to ensure structural integrity and safety under high pressure.
A liveaboard is a boat designed for multi-day scuba diving trips, where divers eat, sleep, and dive from the same vessel.
A logbook is a diver's personal record of completed dives, documenting date, location, depth, time, and conditions.
Marine life interaction refers to a diver’s encounters with underwater creatures, emphasizing observation without harm.
Mask squeeze is a barotrauma caused by failing to equalize the air pressure inside the mask during descent.
A monofin is a single, large fin used in freediving and competitive swimming, where both feet are inserted into foot pockets side by side.
A multilevel dive is a dive where different depths are visited sequentially, often maximizing bottom time using dive computers or tables.
A nautical mile is a unit of measurement equal to 1.852 kilometers or 1.1508 statute miles, used primarily in marine navigation.
The no-decompression limit is the maximum time a diver can spend at a given depth without requiring staged decompression stops.
An octopus is a backup second-stage regulator used to share air with a buddy during an emergency.
Open Water Diver is the entry-level scuba certification that qualifies divers to dive independently with a buddy to 18 meters (60 feet).
An overhead environment is any dive setting where a direct vertical ascent to the surface is obstructed, such as caves or wrecks.
Overweighting refers to carrying more lead weight than necessary when scuba diving, which can negatively affect buoyancy control and safety.
Oxygen toxicity is a condition caused by breathing oxygen at elevated partial pressures, potentially leading to seizures and other symptoms.
Partial pressure refers to the pressure exerted by a single gas within a gas mixture, important for understanding gas absorption in diving.
Peak Performance Buoyancy (PPB) refers to a diver’s ability to achieve perfect trim, neutral buoyancy, and controlled movements underwater.
A pony bottle is a small, independent scuba cylinder used as a redundant air supply for emergencies.
A rebreather is a closed or semi-closed circuit scuba system that recycles exhaled gas by removing carbon dioxide and adding oxygen.
The recreational limit refers to the maximum depth and conditions allowed under standard scuba certification, typically 40 meters (130 feet).
The Rescue Diver course trains divers to recognize, prevent, and respond to diving emergencies, both minor and major.
A reverse block is a condition where expanding air becomes trapped in a diver’s sinuses or ears during ascent, causing pain or injury.
A safety stop is a voluntary pause at 3–5 meters (10–15 feet) for 3 minutes during ascent to allow excess nitrogen to off-gas safely.
Salinity refers to the concentration of dissolved salts in water, affecting buoyancy and equipment performance in scuba diving.
SCUBA stands for Self-Contained Underwater Breathing Apparatus, referring to the system that allows divers to breathe underwater independently.
A scuba cylinder is a high-pressure tank that stores the compressed breathing gas used during a dive.
Scubapro is a leading brand of scuba diving equipment, known for its innovative regulators, BCDs, wetsuits, and dive computers.
A sea cucumber is a soft-bodied marine animal found on the ocean floor, known for its role in recycling nutrients in the ecosystem.
A sea fan is a soft coral with a branching, fan-like structure that provides habitat for marine life and adds color to reefs.
A seal is a marine mammal known for its agility in water, commonly encountered by scuba divers in colder regions.
Sharks are cartilaginous fish found in oceans worldwide, often misunderstood and critically important to marine ecosystems.
A shot line is a rope and weight system used to mark a dive site and provide a visual reference for descent and ascent.
Sidemount is a scuba configuration in which tanks are mounted along the diver’s sides rather than on the back.
A signal tube, also called a surface marker buoy (SMB), is an inflatable device used to signal a diver’s location at the surface.
A silt-out is a condition where fine particles are disturbed and suspended in water, reducing visibility to near zero.
A snap hook is a metal clip used by divers to secure gear to D-rings, preventing equipment loss and improving streamlining.
A snorkel is a breathing tube that allows divers and swimmers to breathe at the surface without lifting their heads.
SNUBA is a surface-supplied diving system that allows users to breathe from a hose connected to a raft, enabling underwater exploration without certification.
Soft corals are flexible, often colorful marine invertebrates that sway with currents and contribute to reef biodiversity.
Spearfishing is an underwater fishing method where divers hunt fish using a spear or speargun while freediving or scuba diving.
An SPG is a gauge used by divers to monitor the remaining air pressure in their scuba cylinder.
Split fins are diving fins with a central split that reduces resistance and increases propulsion efficiency with less effort.
A spool is a compact reel used in diving for deploying DSMBs, marking routes, or conducting searches.
A stage cylinder is an additional scuba tank carried during a dive to extend bottom time or support decompression obligations.
A strobe is a flashing light used underwater for signaling, locating divers, or enhancing night photography.
A surface interval is the amount of time a diver spends at the surface between dives to off-gas nitrogen.
A Surface Marker Buoy is a floating inflatable tube that signals a diver’s location at the surface.
Surge is the back-and-forth motion of water caused by wave energy, often affecting shallow dives near shore.
A swim-through is an underwater passage or arch that divers can safely swim through, often found in reefs or wrecks.
A tank banger is a signaling device used to get a diver’s attention underwater by making noise against the scuba cylinder.
Technical diving goes beyond recreational limits, often involving decompression, mixed gases, and advanced equipment.
A thermocline is a distinct layer in the water column where temperature changes rapidly with depth.
The three-minute stop is a recommended safety stop at 15 feet (5 meters) after a dive to reduce decompression risk.
Tides are the regular rise and fall of sea levels caused by the gravitational pull of the moon and sun.
Time to fly is the recommended surface interval a diver should observe before boarding a plane to avoid decompression sickness.
Tipping in scuba diving refers to the gratuity given to dive professionals for guiding, instructing, or assisting during trips.
Turtles are marine reptiles commonly encountered while diving, known for their graceful movement and calm demeanor.
An underwater compass helps divers navigate by maintaining direction and orientation beneath the surface.
Underwater navigation refers to techniques divers use to find their way and return to specific points during a dive.
Upwelling is the oceanographic process where deep, cold, nutrient-rich water rises to the surface, often enriching marine life.
Viz is short for visibility, describing how far a diver can see underwater, typically measured in feet or meters.
A weight belt is a diving accessory worn around the waist to help offset buoyancy from exposure suits and gear.
Wet notes are waterproof notebooks used by divers to write underwater for communication, navigation, or documentation.
A wetsuit is a neoprene garment worn by divers to provide thermal insulation in cool water.
Whales are large marine mammals occasionally encountered on scuba dives, known for their size, intelligence, and acoustic behavior.
Wreck diving is the exploration of sunken ships, aircraft, or structures as a recreational or technical dive activity.
Wreck penetration is the act of entering a submerged structure during a dive, requiring special training and gear.
A yoke valve is a type of scuba tank valve where the regulator is clamped over the valve using a yoke bracket.
A Z-Knife is a compact cutting tool with a protected blade used by divers to cut line or webbing safely and efficiently.
The zebra shark is a spotted, bottom-dwelling shark commonly found in Indo-Pacific reefs, known for its docile nature.
Zero visibility is a dive condition where underwater visibility is completely obscured, requiring special skills and caution.
A Zodiac is a rigid-hull inflatable boat (RHIB) often used for scuba diving operations due to its speed and maneuverability.
Zooanthids are colonial marine invertebrates resembling soft corals, often colorful and found in tropical reef environments.
