Using a snorkel allows the diver to see below the surface while breathing air from the surface without having to raise the head for each breath. Most modern snorkels are designed to attach to the mask strap on the diver’s left side. Historically many instructors have taught to only mount the snorkel on the left side because when not in use, the snorkel is out of the way so the air hose from the scuba unit always comes over the right shoulder. Most snorkels offered for sale today are designed for the left side and most have one or two valves to aid in clearing out any water. Snorkels used for skin diving are often a rigid tube with mouthpiece. The tube is shaped to fit around your head. If you are using your snorkel for both skin diving and scuba, there should be a flexible portion so when you are on scuba the mouthpiece hangs to the side of your head.
The position of the snorkel above your head is important. If placed too far forward the tip of the snorkel will be in the water when you look down. If this happens while you inhale, you get water instead of air. The ideal position is for the tip of the snorkel to be directly over the top of your head when your face is in the water.
When entering the water on scuba you should use your regulator. Once back on the surface you may switch back to your snorkel. Using a snorkel at the beginning of a dive conserves tank air if there is a long surface swim to the dive site, or an extended surface time waiting for other divers to enter the water. At the end of the dive the snorkel can be used if your tank pressure is low. Snorkel use while swimming on the surface allows for a comfortable swimming position.
When making a skin dive, take a breath and hold it, put some pressure on your ears by holding your nose and exhaling gently, then do a surface dive, clearing your ears as you go deeper. Swim a comfortable distance underwater. Then as you approach the surface, look up and put a hand up to avoid hitting your head on any obstruction. As you reach the surface, wait a second or two for the water in the snorkel to self-drain through the valve, and then blow the remaining water out before cautiously taking the next breath.
The snorkel will add “dead-space” to your normal breathing. You will instinctively increase the volume of air exchanged in your lungs. A snorkel three feet (one meter) long will not work due to increased dead space in the snorkel. As you inhale, with a long snorkel, you will bring back a portion of the last breath you just exhaled. As depth increases, water pressure increases. The lungs are designed to forcefully exhale. Inhalation effort increases dramatically if trying to use a snorkel 20 inches (50 centimeters) or more below the surface. The dream of breathing through a garden hose attached to the surface just doesn’t work. You need scuba to go deeper.
Remember, when making a skin dive, the tip of the snorkel must be in air to inhale that next breath. Snorkeling and skin diving are great ways to enjoy the water just beneath the surface. You are free without the added weight and bulk of scuba, however breathing on scuba underwater gives you more time to spend below. Many divers enjoy skin diving on shallow reefs where there is a tremendous amount of life to see. Some skin divers also enjoy spear fishing and photography.