Ballast / Weight
Gear Additional weight (usually lead) used by the diver to counteract the positive buoyancy of the body and equipment, allowing for descent.
The weighting system can consist of a belt, integrated pockets in the buoyancy compensator (BCD), or technical harnesses. Proper weighting is one of the most difficult skills to master: too much weight increases air consumption and ruins trim, while too little weight prevents performing the safety stop correctly at the end of the dive.
Barotrauma (Squeeze)
Safety Physical damage caused to body tissues by a pressure difference between a body air space (or equipment) and the surrounding gas or liquid.
The most common barotrauma is the middle ear squeeze, which occurs when a diver cannot equalize pressure during descent. Other types include mask squeeze (face squeeze) and tooth squeeze. The fundamental preventive technique is early and frequent equalization (e.g., Valsalva maneuver).
Boyle's Law
Technical A physical law stating that, at a constant temperature, the volume of a gas is inversely proportional to the pressure it receives.
This is the fundamental law of diving: it explains why the air in the lungs, mask, or BCD compresses as you descend and expands as you ascend. It is the technical reason why a diver must never hold their breath during ascent, to avoid pulmonary overexpansion.
Decompression
Technical The process of eliminating inert gases (nitrogen or helium) absorbed by body tissues during a dive under pressure.
In recreational diving, 'no-stop' or 'no-decompression' dives are performed, respecting limits that allow for a direct ascent (though always with a safety stop). In technical diving, mandatory stops at specific depths are planned to allow the body to safely release excess gas and avoid decompression sickness.
Drysuit
Gear Thermal protection equipment that completely isolates the diver from the water using seals at the neck and wrists. It is the standard for diving in Patagonia and Andean lakes.
Unlike wetsuits or semi-dry suits, a drysuit maintains a layer of air between the body and the suit, allowing the use of thermal undergarments beneath. In Argentina, its use is practically mandatory year-round in destinations like Ushuaia and highly recommended in winter for the rest of the Argentine Sea. It requires a specialty course to master buoyancy control through inflating and venting the suit.
Halocline
Environment A physical phenomenon that occurs when layers of water with different salinities meet, creating a visual distortion similar to mixing oil and water.
Haloclines are commonly found where rivers meet the sea or in coastal caves. For the diver, the halocline represents a temporary visual challenge, as the view becomes blurry until the transition layer is completely crossed.
Nitrogen Narcosis
Safety An anesthetic effect caused by the high partial pressure of nitrogen when breathing air at depth. It usually manifests starting at 30 meters (100 feet).
Often called 'the rapture of the deep,' its symptoms include euphoria, disorientation, and slow reflexes. It disappears immediately upon ascending to shallower depths. In technical diving, it is mitigated by using helium-based mixtures (Trimix), which reduce gas density and narcotic load.
Nitrox
Technical A gas mixture that contains a higher proportion of oxygen and a lower proportion of nitrogen than normal atmospheric air. It is used to extend no-decompression limits and reduce fatigue.
Enriched Air Nitrox (EANx) diving allows for longer bottom times by reducing nitrogen absorption in body tissues. It requires specific certification and gas analysis before every dive to determine the Maximum Operating Depth (MOD).
Regulator
Gear A mechanism that reduces high-pressure air from the cylinder to ambient pressure so the diver can breathe naturally.
It consists of two main stages: the first stage (connected to the tank) and the second stage (the mouthpiece from which you breathe). It is the most critical component of diving equipment and requires rigorous annual maintenance by certified technicians to ensure proper function and safety.
Safety Stop
Safety A voluntary pause of 3 minutes at 5 meters (15 feet) depth performed at the end of every dive before surfacing.
While not a mandatory decompression stop according to dive tables, the safety stop is a recreational diving standard that adds an extra margin of safety to allow the body to release accumulated nitrogen and to control the speed of the final ascent to the surface.
Surface Interval
Technical The amount of time a diver spends out of the water between two consecutive dives.
During the surface interval, the body continues to eliminate residual nitrogen absorbed during the previous dive. A proper interval is essential for reducing the risk of decompression sickness in repetitive dives.
Thermocline
Environment A layer of water where temperature changes drastically with depth. Very common in Patagonian lakes and quarries.
In Patagonian lakes, the thermocline can be very sharp, with differences of more than 5°C (9°F) in just a few meters. Visually, it is often identified by a shimmering distortion in water clarity (halocline/thermocline) similar to heat waves over asphalt.
Trim
Technical The horizontal attitude or position of the diver in the water. Good trim minimizes drag and protects the marine environment.
Achieving neutral trim (a perfectly horizontal position) is fundamental in technical and advanced recreational diving. It facilitates efficient finning, reduces gas consumption, and prevents kicking up bottom sediment, which is critical in caves, wrecks, or silty bottoms.
Trimix
Technical A mixture of three gases (Oxygen, Helium, and Nitrogen) used in technical diving for deep dives.
Helium is added to the mixture to reduce the proportion of nitrogen and oxygen, thereby mitigating nitrogen narcosis and oxygen toxicity at great depths (usually below 40-50 meters). It is the standard for deep shipwreck exploration in the Argentine Sea.
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