Terminology 50/50 Nitrox50. 50% O2, 50% N2, commonly used as a Travel Mix. Abdominal Hernia A weakness of the abdominal wall through which the intestines or other intraabdominal contents protrude. Dangerous to a diver if a loop of air-containing intestine is trapped outside the abdomen. Absolute Pressure Absolute pressure is calculated by using a vacuum as the zero point and including the gauge and atmospheric pressure in the calculation. Actual Bottom Time (ABT) Total elapsed time in minutes from leaving the surface until ascent is initiated. AGE Abbreviation for arterial gas embolism. Air A gas mixture containing 21% oxygen, 78% nitrogen and 1% other gases (mainly argon). Compressed air is used for recreational scuba diving. Air Compressor A machine that compresses or pressurizes air; for scuba diving purposes, air is compressed from the atmospheric level (14.7 psi at sea level) to the capacity of the tank, usually between 2500-3000 psi. Air Embolism An air embolism occurs when air enters the bloodstream through ruptured alveoli into the pulmonary capillaries. The air in the bloodstream then forms bubbles, which can block blood flow to the body’s tissues causing serious damage. Air Pressure The force per unit area exerted by the weight of air; at sea level, the air pressure is 14.7 psi. Air pressure decreses with altitude. Alpha Flag International maritime signal flag, meaning "Diver down, keep clear!". Alternate Air Source Any device a diver can use in place of the primary regulator, in order to make an ascent while still breathing normally. Alternobaric Vertigo Dizziness brought on by the inequality of pressures in the inner ear. Altitude Sickness Illness brought on by the sudden reduction in pressure of ascent to altitude. Aluminum 80 Most common tank in the dive industry. Nominal capacity 80 cu. ft. Alveolus Air sac at the terminus of a bronchus where oxygen and carbon dioxide transfer occurs. Ambient Pressure The surrounding pressure; on land, comes from the weight of the atmosphere (see air pressure); at depth, comes from the weight of the water plus the weight of the atmosphere. Analog Instruments Instruments which use a needle or a hand moving around a dial to provide information. Apnea Term used when a person stops breathing. Arterial Gas Embolism Condition characterized by bubbles of air from a ruptured lung segment under pressur; the bubbles enter the pulmonary circulation and travel to the arterial circulation, where they may cause a strok. (AGE or CAGE) Ascent Bottle An extra cylinder of air used in cases of air shortage or on deep dives to allow decompression stops without fear of running out of air. ATA Atmosphere absolute; 1 ata is the atmospheric pressure at sea level; measured with a barometer. Atmosphere The blanket of air surrounding the earth, from sea level to outer space. Also, a unit of pressure; “one atmosphere” is pressure of the atmoshere at sea level, i.e., 760 mm Hg. Two atmospheres is twice this pressure, 1520 mm Hg, etc. Abbreviated atm. Amospheric Pressure Pressure of the atmosphere at a given altitude or location. Back Roll Method of leaving a boat by sitting on its rail and rolling backwards into the water. Bar Short for barometric pressure. The method of measurement oa air pressure used throughout most of the world and by the compressed gas industry. Barometric Pressure Synonymous with atmospheric pressure with the exception that barometric pressure varies according to weather and other conditions. Barotrauma Disease or injury due to unequal pressure between a space inside the body and the ambient pressure, or between two spaces within the body; examples include arterial gas embolism. BCD Garment worn when diving to aid in floatation. Allows the diver to swim or rest without struggling to keep his head above water. Bends A form of decompression sickness caused by dissolve nitrogen leaving the tissues too quickly on ascent; mainfested by pain, usually in the limbs and joints; “the bends” is sometimes used to signify any manifestation of decompression sickness. Bleb An abnormal pocket of air in the lungs, usually under the lining of a lung, that can rupture with ascent and lead to barotrauma. Blue Water Term frequently used to refer to the open ocean, as opposed to lakes or quarries. Body Suits Garment which provides full-length, stylish abrasion protection when diving in conditions where a full wetsuit may not be needed. Body suits provide minimal insulation and may be worn under a traditional wetsuit for added insulation and ease of suiting up. Bottom Time Variable definition; in square wave diving, the time between descending below the surface to the beginning of ascent. In multi-level diving, the time between descending below the surface and beginning the safety stop. Booties Boots worn under diving fins. Bottle Scuba tank or cylinder. Bottom Dump A valve in the bottom of a BC, which allows you to empty air while in a head-down mode. Bottom Mix Mix breathed at the bottom, especially when other gas mixes are used for travel and/or decompression. Bottom mix should have a ppO2 less than 1.4. END is typically chosen to be 99 fsw or 132 fsw. Bounce or Bounce Dive To dive and surface at intervals repeatedly. A dive where you turn around to ascend immediately after reaching the bottom. Boyle’s Law Under constant temperature, the volume of a given mass of gas is inversely proportional to the absolute pressure of the gas. Braille Dive A dive in which the visibility is so bad you have to navigate by touch. Breath-hold Diving diving without life support apparatus, while hoding one's breath. Also known as free diving. BSAC British Sub-Aqua Diving Club Bubble A collection of air or gas surrounded by a permeable membrane through which gases can enter or exit. Buddy A diving partner. Always dive with a buddy...new divers should never dive alone. Buddy Breathing Two divers sharing air from one second stage regulator or one breathing from a safe alternate second stage regulator. Buoyancy Tendency of an object to float or sink when placed in liquid; objects that float are positively buoyant, those that sink are negatively buoyant and those that stay where placed are neutrally buoyant. Buoyancy control is a very important factor in diving safely. Buoyancy Compensator Inflatable vest worn by a diver, which can be automatically or orally inflated to help control buoyancy; abbreviated as BC. Burst Disk A thin copper disk held in place with a gasket and a vented plug, which prevents the pressure in a scuba tank from exceeding the maximum tank pressure normally used. C-Card A C-Card refers to your certification card for you level of achievement. Dive resorts and Scuba Diving centers will not sell you tank fills or dive trips unless you can show them this certification. CAGE Abbreviation for cerebral arterial gas embolism. (See arterial gas embolism) Canister Light Type of dive light where the battery pack is strapped to your belt and teh light is held in your hand. Capillary Depth Gauge A gauge made up of a small-diameter, clear plastic tube, wrapped around a circular dial, with the open end of the tube next to 0 on the dial and closed at the other end. The gauge uses Boyle’s Law to determine depth. Carbon Dioxide CO2; an odorless, tasteless gas that is a byproduct of metabolism; is excreted by the lungs in exhaled air. Important in the control of respiration. Carbon Dioxide Retention Frequent cause of CO2 toxicity, usually from skip breathing. Carbon Monoxide CO; odorless, tasteless, highly poisonous gas given off by incomplete combustion of hydrocarbon fuels. Carbon Monoxide Poisoning Carbon monoxide bonds with blood hemoglobin prevent the blood cells from carrying oxygen. The strong bond between hemoglobin and CO causes oxygen deprivation in the tissues and in extreme cases can cause death. Cattle Boat Term used to describe a crowded dive boat, where the divers are like a herd of cattle. Chamber Hyperbaric chamber, for diagnosis and treatment of decompression sickness. Chemical Light Stick The stick is a light source in which the two chemicals inside the stick mix to produce light. Divers attach these sticks to their tank valves or snorkels to increase the ability to be seen by other divers on night dives. Chokes A form of decompression sickness caused by enough bubbles entering the lungs to interfere with gas exchange; manifested by shortness of breath and can be fatal. Chumming Term used for attracking sharks with a mixture of blood and fish parts. Also used to describe vomiting overboard from seasickness. Clearing Techniques Techniques for equalizing the Eustachian tubes while descending and ascending during a dive. Closed Circuit Scuba (Rebreather) Apparatus designed to allow divers to re-breathe exhaled air after the removal of CO2 and the addition of supplemental O2. In contrast to “open circuit”, closed circuit scuba is noiseless and creates no bubbles. Cold Water Near-Drowning Drowning associated with cold water and hypothermia. Coral Invertebrates that secrete an internal, hard skeletal structure composed of calcium carbonate, which is absorbed from the surrounding water. Core Temperature Core temperature is the internal temperature of the body. 98.6 degrees is the normal internal temperature of the human body. Deviation from this temperature by even a few degrees either way for more than a short period may be life threatening. Decompression Any change from one ambient pressure to a lower ambient pressure; always results in a reduction of gas pressures within the body. Decompression Dive Any diver where the diver is exposed to a higher pressure than when the dive began; decompression occurs as the diver ascends. Decompression Illness (DCI) Relatively new term emcompassing all bubble-related problems arising from decompression, including both decompression sickness and arterial gas embolism. Decompression Schedule Specific decompression procedure for a given combination of depth and bottom time, normally indicated as feet/minutes. Decompression Sickness (DCS) General term for all problems resulting from nitrogen leaving the body when ambient pressure is lowered. Can be divided into Type I (musculoskeletal and/or skin manifestations only) or the more serious Type II (neurologis, cardiac and/or pulmonary manifestations). Decompression Stop On ascent from a dive, a specified time spent at a specific depth, for purposes of nitrogen off-gassing; when not mandatory it is called a safety stop. Also known as the depth at which a diver must stop on ascent for a specified period in order to eliminate inert gas before continued ascent. Dead Reckoning Navigating without using external referents, using compass, initial known position, and estimates of speed, current, wind, etc. De-fizzing Off-gassing. Deep Diving For recreational divers a deep dive is one with a maximum depth of 130 feet / 39 meters. Defogging Solution The solution is a substance rubbed on the inside of the scuba mask, such as saliva, which prevents fog from building up inside the mask. Dehydration Condition where the water content of the body is reduced; caused by immersion, alcohol, medications, ecessive loss of fluids from vomiting and diarrhea or decreased intake of fluids. Depth Maximum depth in fsw attained during a dive. Depth Gauge A depth gauge a device that indicates how far a diver is below the surface of the water. Descent/Ascent Line A line suspended from a boat of buoy which is used by divers to control their rate of descent or ascent. Deserved Hit DCS occuring after violating table or computer limits. Diaphragm Regulator A diaphragm first-stage design inherently prevents water from entering the first-stage mechanism itself. This helps to prevent internal corrosion and contamination buildup, which may lead to more consistent performance between service intervals. Digital Depth Gauge Depth gauge which automatically provides a readout of both the current and maximum depth reached during a dive. Digital Instruments Digital Instruments provide a numerical display of information. DIN Valve Alternative to a yoke fitting for first stage. Screws in rather than clamping on; o-ring is "captured" inside the valve, reducing the chance of o-ring failure. Dive Computer Small computer, carried by the diver, that constatly measures water pressure (and hence depth), and time; based on a pre-programmed algorithm, the coputer calculates tissue nitrogen uptake and elimination in several theoretical compartments and provides a continuous readout of the dive profile, including: depth, elapsed time of dive, duration at current depth before decompression becomes mandatory and a warning if the rate of ascent is too fast. Dive Dry Diving in a dry suit. Dive Flag A dive flag may be either a red rectangle with a diagonal white stripe or a blue and white double tailed pennant. These flags are used to warn watercraft and skiers to stay away because there are divers in the water. Dive Lights Specially designed underwater lights used for night dives or dive in dark places such as wrecks or caves. Dive Tables Printed collection of dive times for specific depths, by which the diver can avoid contracting DCS. Most tables are based on Haldanian theory for nitrogen uptake and elimination. Drift Dive A dive in which a non-finning diver is carried along by the current. Double-Disking Using 2 burst disks on the valve of your tank to decrease the chance of losing all your air. Double steel 104's Pair of steel cylinders with a nominal capacity of 104 cu. ft. connected together with bands and a manifold. D-Rings D-shaped rings. Attach to BC webbing with weight retainers. Drift Deco Hanging from a lift bag or DSMB during your decompression time (usually used for high currents). Dry Suit Water-tight garment that keeps the diver’s body warm by providing insulation with a layer of gas, such as air; for diving in waters that are too cold for comfortable wet suit protection, usually below 65°F. Dual Regulator Systems Dual regulator systems use two regulators on a single air supply to allow a diver access to continue to access his air supply in the event of a malfunction in the main regulator. Dual Tank Manifolds A dual tank manifold is used for double cylinder systems. It has two valves similar to single tank systems which are attached by a heavy-duty crosspiece with a valve outlet in the center. Dual-Valve Manifold A dual-valve manifold allows a single cylinder system to utilize two regulators on a single scuba tank. EAN Enriched air nitrogen; nitrox ENT Ear, Nose and Throat conditions and/or diseases. Entonox Mixture of nitrous oxide and oxygen (50-50). Dangerous to administer to divers. Equalization Equalization is the act of forcing air into an open space to offset increasing hydrostatic pressure. This can be applied to such spaces as a dive mask or the diver’s ears, and prevents what is known as a squeeze. First Stage The part of the regulator which attaches to the scuba tank valve that lowers the tank pressure to ambient pressure + a pre-determined pressure (e.g., ambient + 140 psi). The term can also refer to the first part of stage decompression. Fins Worn on the feet to increase maneuverability and allow for faster swimming. Foul the Hook To tie the wreck hook upside down to facilitate leaving the wreck. This is usually done by the last person to ascend from the wreck. Free Diving Variably defined; in some usage, diving without any scuba or other equipment and synonymous with breath-hold diving; in other usage, diving without any attachment to the surface, and therefore including scuba diving. FSW Feet of sea water; used to indicate either an actual depth or just a pressure equal to that depth (e.g., in a hyperbaric chamber. Gas Absorption and Elimination Dissolved gases such as nitrogen are absorbed into the blood and tissues during the course of a dive. The level of saturation depends on the depth of the dive. The elimination of these gases is very important in preventing decompression sickness. The length of time required for elimination depends on the duration and depth of the dive. Gas Laws Laws that predict how gases will behave with changes in pressure, temperature and volume. Gas Saturation Gas saturation occurs when the level of dissolved gas in a body tissue has reached its maximum. Gauge Pressure Pressure exclusive of atmospheric pressure; when diving, gauge pressure is due solely to water pressure. Golden Triangle The area between the chin and nipples where it is easiest to access equipment such as knives or regulators. Half Time Half the time it takes for a dissoved gas in a tissue (such as nitrogen) to equilibrate to a new pressure, or to reach full saturation at a new pressure. Theoretical tissue half times are used in designing dive tables and algorithms for dive computers. Hazardous Marine Life Living creatures in the marine environment that are dangerous or harmful to the diver. Heliox Mixture of helium and oxygen, used for very deep diving. Helium Second lightest gas; does not cause problems of narcosis seen with nitrogen, and is therefore used for very deep diving. Hoods Hoods are garments worn to provide thermal and abrasion protection to a diver’s head. HP Hose High Pressure Hose. Goes from the regulator 1st stage to the air pressure gauge. H-Valve A tank valve with 2 outlets. Hydro Hydrostatic testing for tank integrity. Hydrogen Hydrogen is an inert gas and the lightest, most abundant gas in the universe. It is believed it could be used as a substitute for helium in deep commercial and military diving. Hydrostatic Test This is a pressure test in which the tank is filled with water instead of air and raised to a pressure five thirds of the maximum working pressure, causing the water to expand and be displaced. If the levels of water displaced are within acceptable limits, the tank passes. If the tank does not pass the test, it may not be refilled. Hyperbaric Chamber Air-tight chamber that can simulate the ambient pressure at altitude or at depth; used for treating decompression illness. IANTD International Association of Nitrox & Technical Divers. Ingassing Taking on additional nitrogen (and/or other inert gasses). J-Valve A J-Valve contains a spring-loaded that, if activated, will shut off a diver’s air supply when the diver reaches a certain tank pressure – usually 300 psi / 20 bar. K-Valve A K-valve is a simple on / off valve. Lift Bags Lift bags resemble small hot air balloons. After being tied to an object to be lifted, the balloon is inflated with air from an extra second stage or special inflation tool and rise to the surface. Live Aboard Dive boat with sleeping and eating accommodations. Commercial liveaboards are usually between 50 and 130 feet long, and can carry anywhere from 10 to 30+ divers for a week or more. Log Books Log books act a a diary of a person’s dive history. They provide tangible evidence of the depth and breadth of a diver’s experience. Log books are generally required on charter dive boats. LP Hose Low pressure hose. Runs from the regulator 1st stage to the 2nd stage or inflator. Lung Squeeze Lung squeeze occurs when breath-hold dives are performed to great depths. The pressure causes the lungs to be compressed beyond the smallest natural volume of the lungs. M-Value An M-value is used in conjunction with a dive computer to express the tissue compartment’s maximum allowable pressure in feet of seawater absolute (fswa). Manifold Plumbing to connect 2 tanks so that one regulator can access gas in both tanks. Marker Buoys A means of locating objects under water. The buoy is simply tossed overboard and the weighted line unrolls and anchors itself to the bottom near the object being marked. Mask Squeeze Mask squeeze occurs in rapid descents where the diver neglects to equalize his mask. The increasing hydrostatic pressure forces tissues surrounding the eye to swell into the uncompensated air space in the mask to fill the reduced volume. Middle Ear Air-containing space of the ear bordered on one side by the tympanic membrane, which is exposed to any change in ambient pressure. Air pressure in the middle ear space can only be equalized through the eustachian tube, which connects the middle ear to the back of the nose. Mix A mixture of gasses, often a trimix. Mixed Gas Variably defined; basically, any non-air mixture (e.g., nitrox), although some authors use the term only for mixes that contain a gas in additons to (or in place of) nitrogen (e.g., helium). Multilevel Diving Multilevel diving involves spend a period of time at several depths on a single dive. Narced Nitrogen narcosis; being under the influence of nitrogen while diving. Narcosis Depressed mental state, anywhere from confusion or drowsiness to coma. Nasal Congestion Swollen, blood-filled linings of the nose and sinuses, often due to allergies. NAUI National Association of Underwater Instructors. Nitrogen Inert gas that makes up 78% of air. Nitrogen is inert in that it does not enter into any chemical reaction in the obdy, but it can cause prblems under pressure (see nitrogen narcosis, decompression sickness). Nitrox Any mixture of nitrogen and oxygen that contains less than the 78% nitrogen found in ordinary air. NOAA National Oceanic and Atmospheric Association. OEA Oxygen enriched air; nitrox. Ocky British term for octopus. Octo Abbreviated term for octopus. Octopus An extra second stage regulator used by your diving buddy in an out of air emergency. Offgassing Reducing the load of nitrogen (and/or other inert gasses). Also known as outgassing. Oil-filled Depth Gauge These are the most widely used depth measuring devices. They are usually found in ready-made instrument consoles. Open Circuit Scuba Apparatus used in recreational diving; exhaled air is expelled into the water as bubbles; no part is re-breathed by the diver. Oxygen Gas vital to all life on this planet; makes up 21% of air by volume. Oxygen Toxicity Damage or injury from inhaling too much oxygen; can arise from wither too high an oxygen concentration or oxygen pressure. The first manifestation of oxygen toxicity while diving can be seizures. PADI Professional Association of Diving Instructors. Partial Pressure Pressure exerted by a single component of a gas within a gas mixture or dissolved in a liquid. Pony Bottles These are small scuba cylinders strapped to a diver’s main tank. These tanks have their own first and second stages and are often used as an alternate air source. Prescription Dive Mask Special masks for divers needing refractive correction. Pressure Any force exerted over an area (see atmospheric pressure, ambient pressure). Pressure Terminology Pressure terminology is the list of terms commonly used to describe pressure. These terms include: atmospheric pressure, barometric pressure, gauge pressure and absolute pressure. PSI Pounds per square inch; a common measurement of air pressure. Purge Valve Purge valves allow masks and even regulators to be cleared easily without having to remove the mask from the diver’s face or the regulator from the diver’s mouth. Recreational Dive Planner The planner is a standard set of tables that give generous dive times and allows divers to plan dives while avoiding decompression sickness in all conditions. Recreational Scuba Diving (RSD) Diving to prescribed limits, including a depth no greater than 130fsw, using only compressed air and never requiring a decompression stop. Reg Abbreviation for regulator. Regulator Regulators allow divers to breath comfortably underwater, at ambient pressure while the air source is a tank of highly compressed air. Repetitive Dive Any dive done within a certain time frame after a previous dive; variable definition exists as to what tie grame constitutes “repetitive”. With some tables, any dive within 12 hours of a previous dive is considered repetitive; when using a computer, any dive whose profile is affected by a previous dive is considered repetitive. Residual Nitrogen Nitrogen that remains dissolved in a diver’s tissues after surfacing from a dive. Residual Nitrogen Time (RNT) The time it would take to off-gas any extra nitrogen remaining after a dive; in dive tables, RNT is designated by a letter A through Z. Residual nitrogen time is always taken into consideration in determining the safe duration for any repetitive dive. Reverse Block When the internal pressure of an air space is greater than the external pressure. Reverse Squeeze Pain or discomfort in an enclosed space (e.g., sinuses, middle ear, inside mask) on ascent from a dive. Rule of Thirds An air management technique. Use a third of the tank to get to your destination, a third to get back, and the last third belongs to your buddy in case of an emergency. Safe Second Octopus. Safety Stop On ascent from a dive, a specified time spent at a specific depth, for purposes of nitrogen off-gassing; by definition it is not mandatory for safe ascent from the dive. Compare with decompression stop. Saturation Diving Diving performed after the body is fully saturated with nitrogen; to become fully saturated, the diver must stay under water for a much longer period than is allowed in recreational scuba diving tables. Scooter Diver Propulsion Vehicle. SCUBA Self-Contained Underwater Breathing Apparatus. Sea Level The level of the world’s oceans; all oceans are at sea level. Sea Sickness Motion sickness or mal de mer. Second Stage The part of the regulator you put into your mouth to breath through. Shallow Water Blackout A sudden loss of consciousness from hypoxia that occurs among some free divers. Often occurs near the surface after a deep dive, hence “shallow water”. Same as latent hypoxia. Shivering Shivering is the body’s attempt to crate heat through muscular activity. Shivering means the body is losing hear faster than it can create it. Shoot the Bag To send a liftbag up with a line attached for a floating decompression stop. Single Dive Any dive conducted at least 12 hours after a previous dive. Sinus Squeeze Sinus squeeze occurs during a rapid descent when a diver is unable to equalize the air space in the sinus cavity. A diver experiencing sinus squeeze will often experience pain and surface with blood in his mask due to the trauma caused by a squeeze. Sinuses Air spaces within the skull that are in contact with ambient pressure through openings in the back of the nasal passages. Silt-out A complete loss of visibility caused by silt being disturbed, typically by careless finning. Skin A thin exposure suit, typically made of Lycra and used in warm water diving. Skin Diving Another term for breath-hold or free diving; diving without the use of scuba equipment. Snorkel A tube used for breathing while floating on the water's surface. Sling Bottle A stage bottle generally used for decompression. Spears Spears are weapons used to hunting fish under water. Spears range from simple pole spears to complex bands to pneumatic-powered guns. Square Dive A dive in which you stay at the deepest point for the duration of the dive. Submersible Pressure Gauge These gauges are a means for divers to monitor their air supply during the course of a dive. Sunburn Pathological damage to the skin from the ultraviolet rays of the sun. Surface Interval Length of time on the surface, usually out of the water, between two consecutive dives. Surface-Supplied Compressed Air Diving Diving with the air continuously supplied by a compressor on the surface; can be used for both sport and professional diving. Thermocline Thermoclines are abrupt transitions to colder water. They occur when warmer, lighter water forms a layer above a more dense, colder layer of water. Tie In To attach the wreck hook to the wreck using a separate line. Tissue A part of the body characterized by specific characteristics, such as muscle, bone or cartilage. The term is also used to refer to any part of the body with a specific half time for loading and unloading nitrogen; in this latter context a tissue may be contiguous or non-contiguous, or even a theoretical compartment. Top-to-Bottom Underwater visibility that is so good you can see the wreck and bottom contours from the surface. Trimix Breathing mixture of composed of three gases, usually helium, nitrogen and oxygen. The composition is denoted as percentage of oxygen / percentage of helium, e.g. 17/50 is trimix with 17% oxygen, 50% helium and the balance (33%) nitrogen. Used for very deep diving. TUP Transfer Under Pressure. A TUP system mates a portable compression chamber to another chamber in order to transfer a person from one chamber to another while under pressure. Underwater Photography The act of photographing objects underwater. This popular hobby requires the use of special waterproof equipment. Vertigo Vertigo (dizziness) is a sign of ear barotrauma and should not be ignored. Causes may range from minor ear squeeze to perforation of the eardrum to inner ear barotrauma. It should be taken seriously and a physician should be consulted. Visibility Visibility is the distance a diver can see underwater measured in feet or meters. V Weight A V-shaped lead weight designed to fit between tanks behind a backplate. Wall Diving Wall diving occurs on rocks or reefs that run nearly vertical, usually from shallow depths to hundreds of feet. Water Pressure Force per unit area exerted by the weight of water; each 33 feet of sea water exerts a pressure equivalent to one atmosphere or 14.7 psi. Weight Belt Belt containing a set of lead weights that is worn around the waist of the diver to make descending easier and to prevent the diver from surfacing involuntarily. Weight Retainer A small metal or plastic device used to keep lead weights from sliding. Wet Suits Wet suits are the most common for of thermal and abrasion protection used by divers. They come in a wide variety of styles and thicknesses that can be used in a variety of environments. Wreck Hook An anchor with bendable tines, used to attach a surface vessel to a wreck. Also known as a grappling hook. Y Valve A tank valve with two outlets.