Equipments

Diving equipment depends on the location of the dive, but whether scuba diving or snorkeling, recreational divers need several basic items. Which are a mask, snorkel, fins, suits and air source devices. 

A diving mask that covers the nose and eyes enables the diver to see while underwater. A snorkel is a tube that allows the diver to breathe while floating at the water's surface. Fins that are worn on the feet let divers propel themselves through the water. 

Divers lose body heat 60 times faster underwater than on land, because water conducts heat much more efficiently than air does. To stay warm, scuba divers wear either a wet suit or a dry suit, depending on water temperature. Wet suits are usually worn in warm-water climates. A wet suit is made of neoprene rubber and absorbs and traps a thin layer of water, which the diver's body quickly heats. In areas such as the North Atlantic or Pacific oceans, where water temperature drops below 10° C (50° F), divers wear dry suits to keep from freezing. A dry suit is made of waterproof materials that keep a diver completely dry. If water temperatures are extremely low, divers wear extra clothing underneath the suit. 

To breathe underwater, scuba divers wear a metal tank filled with compressed air, and a regulator that attaches to the tank. The regulator reduces the pressure of the air to match the surrounding water pressure, so that the diver can breathe the air comfortably. The regulator also distributes the air among four hoses. One hose delivers air to a mouthpiece, through which the diver inhales and exhales. Another hose from the regulator attaches to an adjustable air bladder called a buoyancy compensator (or control) device (BCD or BC), which the diver wears as a vest. By adding air to the BCD, the diver becomes more buoyant and rises. By releasing air, the diver becomes less buoyant and sinks. With minor adjustments of air, the diver can achieve neutral buoyancy. A third hose attaches to pressure gauges that divers use to monitor how much air remains in the tank. A fourth hose attaches to a backup breathing device called an alternate air source, or octopus.

Divers also wear a belt with lead weights to help them descend and stay underwater. The weights are spaced evenly around the belt for balance. Most divers carry from 5 to 20 lb (2.3 to 4 kg) of weight, depending on their body weight, the suit they are wearing, and where they are diving (buoyancy is greater in saltwater than in fresh water). A quick-release buckle enables the diver to shed the belt and rise to the surface in an emergency. 

Emergency equipment includes a dive knife, in case the diver becomes entangled in fishing line or marine plants, and whistles, lights, or signaling devices, in case the diver is lost or swept out in a current. Divers should also have a tank of oxygen onboard, along with a marine radio and a first aid kit.

Submersibles
  
Submersibles are pressurized vehicles that maintain surface air pressure inside while they descend deep into the ocean. The most common type of submersible is a submarine. Smaller submersibles are used in deep diving to transport hard-hat divers to and from workstations. Submersibles are used in deep-sea exploration, scientific studies, and military operations.

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