Diving has its own terminology and language. Below are some examples you should know.
- SCUBA or scuba is short for self-contained underwater breathing apparatus. Typically, scuba equipment consists of a cylinder containing compressed breathing-grade gas with the moisture extracted. For this reason, it is recommended you hydrate well before diving.
- Open circuit (OC) is the most common form of scuba equipment. Using OC, you inhale breathing gas from your cylinder via a scuba regulator and exhale gas into the water.
- Rebreather reuses the exhaled gas, which filters through a scrubber to enable the air to be recycled. Oxygen is added to the gas as part of the recycling process. Some of the advantages of diving while using a rebreather include longer bottom time, fewer bubbles, and the potential to dive deeper for longer. There are many types of rebreathers on the market, and each one requires specific training.
- Air/Nitrox is air with an increased percentage of oxygen, typically 32% or 36%. (Normal breathing air consists of approximately 78% nitrogen, 21% oxygen, plus various other trace gases.) The increased oxygen percentage used in Nitrox can reduce the risk of decompression sickness. Other benefits of using Nitrox are that it allows for more dive time and less surface interval time and may improve your respiratory rate. There are, however, specific risks when using Nitrox, and additional training is required to use this gas.
- No decompression limit (NDL) is the maximum allowable dive time a diver can remain at a specific depth and ascend directly to the surface without requiring decompression stops. (Note: Decompression diving has specific risks and specialized equipment. Further training is required.) Decompression will be discussed later in the course, including the use of dive computers to monitor your NDL.
- Safety stop is a recommended stop for 3 to 5 minutes at 5 meters/15 feet. It is recommended that safety stops are completed for all dives. Note: This is not a decompression stop; it is an additional safety recommendation before actual decompression is required. Most modern dive computers will build in a safety stop.
- Buddy is a certified dive friend. You should always dive with a buddy so that you can watch out for each other and share the experience. Always stay within close contact with your buddy (3 meters/10 feet in average conditions) and definitely maintain visual range at all times. The buddy system is a safer way to dive because it gives you assistance if you need it. You also have two minds to solve underwater tasks. Decide before the dive who will be the main leader and then swim alongside each other to stay together.