One of the first things that a scuba diver is taught in a certification class is about the equipment they are going to use. While there are pieces of equipment that you may only need on certain types of dives (like a dive light), it is essential to carry some items on every dive, such as a Buoyancy Control Device (BCD), air tank, a regulator, a dive mask and fins.
Exposure suits come in three types: bodysuits, wet suits and dry suits. Bodysuits can only be used in warm, tropical waters. They provide protection from sun exposure, scrapes and cuts, but they offer no insulation. Wet suits are used in tropical and temperate water. Depending on the thickness of your suit, they can provide warmth in water temperatures as low as 50 degrees Fahrenheit. They work by trapping a small layer of water between the suit and your skin, which your body then warms. A dry suit is used in cold waters and is called a dry suit because they keep divers completely dry.
A scuba unit consists of a tank, a BCD and a regulator. The scuba tank stores compressed air, which the diver breathes. Typically, they are made from steel or aluminum. The BCD holds the tank to your back and has an air bladder that you can fill or empty to help control your buoyancy in the water. If you add more air to your BCD, you become more buoyant. The regulator takes the high-pressure air that is in your tank and adjusts it to allow you to breathe. This is done via a mouthpiece most commonly referred to as the second stage (the first stage is the part of the regulator that connects to the tank). The regulator will also route air to your BCD and to your instruments, like your submersible pressure gauge (SPG), which tells you how much air you have left in your tank.
Weights and Belt
Another way that divers control their buoyancy in the water is with weights. In saltwater, with a wet suit on, most people become more buoyant, even with all the heavy dive equipment. Because of this, you need weights to help you descend. How much weight a diver uses will depend on a number of factors, such as the diver's body mass and how experienced the diver is. The weight is typically distributed evenly around a belt the diver wears around the waist, although some BCDs have integrated weight systems.
Mask, Snorkel and Fins
The mask allows divers to see clearly underwater. According to the Professional Association of Diving Instructors (PADI), they work by creating a small air pocket. The snorkel is a tube through which divers can breathe when swimming on or near the surface. This is a great option if you have to swim to or from shore for a dive and don't want to waste your air on the swim to the dive point. Fins help divers to utilize their leg muscles to swim through the water. Fins come in two styles, open heel or full foot. Full-foot fins aren't adjustable and are not as common as open-heel fins. Open-heel fins have adjustable straps, but divers must also wear dive boots with open-heel fins in order to protect their feet in most diving situations.