Diving Glossary | Essential Terms Every Beginner Should Know
Once you start diving, a lot of unfamiliar terms show up in your course and in conversations with the shop. This article groups the essential terms every beginner should learn into four categories: certification, safety management, gear, and underwater technique.
In short, getting a handle on just four terms — C-card, buddy system, neutral buoyancy, and decompression sickness — makes your course content much easier to follow.
What Terms Come Up Around Certification and Courses?
- C-card (Certification Card): a certification card issued by an organization like PADI. Not a government license, but treated in practice as essentially required to dive
- Open Water Diver (OWD): the entry-level license you get first. Certified to a maximum depth of 18m
- Advanced Open Water Diver (AOW): the second-step license, extending your depth limit to 30m
- Specialty: additional courses focused on a specific theme, like drysuit, night diving, or deep diving
- Fun diving: not a course — regular diving where a certified diver with a C-card enjoys the sea alongside a guide
What Terms Come Up Around Safety Management?
- Buddy system: the basic diving rule of moving in pairs of two or more, checking on each other's safety throughout the dive
- Decompression sickness (DCS): a diving illness caused when nitrogen dissolved into your bloodstream underwater turns into bubbles as you ascend. Ascending too fast or an unreasonable dive schedule are the main causes
- No-decompression limit (NDL): a rough guide to how much time is left before you'd need a decompression stop to ascend safely. Shown on a dive computer
- Safety stop: pausing for a few minutes at around 5m depth before surfacing, to let the nitrogen in your body settle before you ascend
- Ear equalizing: adjusting the pressure inside your ear to match changing water pressure. Covered in detail in "Diving Ear Equalizing Tips"
What Terms Come Up Around Gear?
- BCD (Buoyancy Control Device): gear that adjusts your buoyancy underwater by adding or releasing air
- Regulator: gear that reduces the tank's high-pressure air down to a breathable pressure and delivers it
- Octopus: a backup mouthpiece on the regulator, for emergencies like a buddy running out of air
- Weight: added weight to help you sink, adjusted to match your body and your suit's buoyancy
- Drysuit / wetsuit: diving suits chosen based on water temperature. See the difference in detail in "A Beginner's Diving Gear Guide"
What Terms Come Up Around Underwater Technique?
- Neutral buoyancy: maintaining a state where you neither sink nor rise underwater, as if suspended in mid-air. A skill that hugely affects how comfortable diving feels
- Fin kick: your propulsion technique underwater using fins. The basic approach is a large, slow motion rather than a rapid flutter kick
- Entry / exit: entering the water and getting out of the water, respectively
- Mask clear: the basic skill of expelling water that's gotten into your mask by exhaling through your nose
- Hand signals: used since you can't talk underwater. "OK," "air remaining," "ascend," and others are always taught early in your course
Summary
Diving terminology can look intimidating at first glance, but in practice it's all practical knowledge for diving safely and comfortably. If you're about to take a course, bookmark this article and come back to it whenever an unfamiliar word comes up.
Frequently Asked Questions
Q. Are a C-card and a license the same thing?
A. What's commonly called a "license" is, in fact, a C-card. It isn't a government license — it's a certification card issued by an organization like PADI.
Q. What does neutral buoyancy actually feel like?
A. It's maintaining a state where you neither sink nor rise underwater, as if suspended in mid-air. It's a fundamental skill that hugely affects how comfortable diving feels.
Q. Why does decompression sickness happen?
A. It occurs when nitrogen that has dissolved into your bloodstream underwater turns into bubbles as you ascend. Ascending too fast or an unreasonable dive schedule are the main causes.
Q. What is the buddy system?
A. It's the basic diving rule of moving in pairs of two or more, checking on each other's safety throughout the dive.
Q. Do I need to memorize every term before I can dive?
A. You don't need to memorize them by rote. They're taught alongside the actual actions during your course, so you'll naturally pick them up as you dive.