Here’s the text version:

A – Air. Most SCUBA tanks are filled with compressed air, which is filtered and dehumidified. Which means it’s probably safer to breathe than the polluted air outside or near a cigarette smoker. It’s dry af, but considering you’re BREATHING UNDERWATER I’d say it’s something we can all learn to live with. Normal breathing air contains a blend of oxygen, nitrogen, argon, carbon dioxide, neon, krypton, ozone… it keeps going. Suffice it to say, divers typically live by the 21-79 philosophy: air is 21% oxygen and 79% nitrogen. (See also, EANx, HELIOX, and TRIMIX).

B – Balanced Regulator. A balanced regulator breathes the same at any depth and with any amount of pressure in your scuba tank. Because they are a more complicated piece of gear, they tend to be more expensive than unbalanced regulators. (See also, UNBALANCED REGULATOR)

C – Computer. Do you remember learning dive tables? Do you remember hating it? That’s why we have dive computers. They allow you to dive longer and more safely. The computer will keep track of your dive time, your ascent rate, and your depth. Some will also keep track of your air supply. Various types of computers can do different things. Buy one. They’re amazing.

D – DIN Regulator. A DIN regulator screws into the DIN tank valve. This regulator has an O-ring where it attaches to the scuba tank. DIN valves are used on higher pressure tanks. DIN is also more common in technical diving. DIN stands for “Deutsche Industrie Norm”. (See also, YOKE REGULATOR)

E – EANx. Enriched Air Nitrox, or EANx, is a blend of oxygen and nitrogen with a higher percentage of oxygen than normal air. In order to utilize nitrox, you’ll need to take a specialty course. Basically, nitrox blends can allow you to stay down longer and to shorten your surface intervals. Some divers say it keeps them from feeling as tired after a dive. EANx poses a different set of parameters and dangers than diving regular air, so be sure to set up your course with a reputable dive center. PS, recreational diving limits nitrox blends to 40% oxygen. (See also, AIR)

F – Fins. If you’ve ever tried to move through the water in scuba gear without fins, you have come to understand their value. Fins can come in open-back or full-foot style, with numerous varieties and functions.

G – Gauge. The pressure gauge, also called the SPG (“submersible pressure gauge”), displays how much air is left in your tank. This may be a mechanical gauge attached to your tank with a hose, or may be built into your snazzy dive computer. (See also, COMPUTER)

H – Heliox. Heliox is a blend of helium and oxygen used for diving greater than 200 feet. This mix is mostly used by commercial and military divers.

I – IP. Internal pressure, or IP, describes the reduced internal pressure between the first and second stages of the regulator. (See also, REGULATOR)

J – J-valve. The J-valve has a lever that essentially blocks 300 psi in the tank. Adjusting the lever allows the diver access to the 300 pounds in reserve. It’s sort of a backup system that was used before gauges offered an emergency indicator when your air is running low. (See also, K-VALVE)

K – K-valve. The K-valve is the standard valve you’ll see on most scuba tanks. The handle is turned on and off to open or close air flow. (See also, J-VALVE)

L – Live aboard. A live aboard puts you in the company of other divers with experienced crew members and lots of diving. You’ll stay on the water for some length of time – it’s similar to a cruise but without the land excursions. I haven’t experienced a live aboard vacation yet but it is high on my bucket list!

M – Martinis Law. Also called the Martini Effect, this affectionately coined term is used to describe the effects of nitrogen narcosis (a phenomenon experienced by some divers at deeper depths). Some people describe being “narced” as being similar to feeling drunk. So Martinis Law states that every 30 feet of depth is the equivalent of drinking one martini. I don’t know that I agree with this in any way, but whatever floats your martini glass.

N – Neoprene. Neoprene is a synthetic polymer used to make wetsuits. Wetsuits are made from foamed neoprene, which contains small nitrogen gas bubbles. Heat is lost through a slow diffusion process, as the nitrogen gas has a very low thermal conductivity. (See also, WETSUIT)

O – Octo. Now called “safe second”, the octopus, or octo, is usually brightly colored so it is easy to spot. It can be a secondary regulator, or even integrated into your BC. I’ve never understood why it’s called an octopus. Or maybe I’ve never understood why we don’t breathe out of cephalopods. Who knows. (See also, REGULATOR)

P – Pony. A pony bottle is a redundant air delivery system. It should never be factored into your dive plan, but is a good backup to your backup plan (which is your dive buddy). Ponies are typically smaller air bottles, colored a popping bright yellow so they are easy to see. PS, when traveling by air, should you decide to take the pony along, you will need to empty it and remove the valve. You can buy a plug for the bottle.

Q – Quick release. This is a function of buckles, weight pouches and hoses, enabling rapid release in the case of an emergency.

R – Regulator. The regulator is how you’re able to breathe from your tank underwater. Regulators come in many different flavors, but the basic setup is the first stage (where it connects to the tank), the air hose, and the second stage (the piece from which you breathe). Regulators can be balanced or unbalanced, and use a piston or a diaphragm. (See also, DIN and YOKE)

S – SCUBA. The acronym SCUBA stands for Self-Contained Underwater Breathing Apparatus. The first self-contained unit was developed in 1876, although humans used to be pretty creative about finding other ways to visit beneath the surface.

T – Trimix. Trimix is a blend of nitrogren, oxygen, and helium. This mix can be blended with as little as 18% oxygen, and can be used to a depth of 200 feet.

U – Unbalanced Regulator. An unbalanced regulator is slightly harder to breathe off of as the tank is being emptied and at depth. It is also less expensive than a balanced regulator. (See also, BALANCED REGULATOR)

V – Valsalva maneuver. This is a technique used by divers to equalize their ears. By gently squeezing your nose and blowing without breathing through your mouth, the pressure forces the middle ear tubes open, enabling them to equalize at depth.

W – Wetsuit. Wetsuits are made from neoprene and are used to keep a diver warm and to offer some exposure protection. Water is allowed into the suit, which is warmed by your body heat and kept close to you with the snug-fitting material. Wetsuits typically run in 3 mm, 5 mm, and 7 mm thicknesses. They also come in different styles, such as full suits, shorties, and farmer johns. (See also NEOPRENE, FARMER JOHN)

X – Xenon light. Xenon bulbs are durable and inexpensive, lasting a bit longer than halogen bulbs. The lights tend to dim as the batteries run low, so divers can tell when it’s time to change them.

Y – Yoke Regulator. This type of regulator fits over the top of the tank valve and is tightened using a screw fitting. Yoke valves have an O-ring fitted to seal the regulator to the scuba tank. (See also, DIN REGULATOR)

Z – Z-knife. A knife with a specialized blade for cutting fishing line or netting.

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