Along with the mask, it was the first piece of dive gear invented. The snorkel allowed the user to breath underwater (albeit only a few inches) and take in the grandeur of the underwater world.
BASIC PRINCIPLE
At its most basic level, the snorkel is simply a tube that allows you to breath surface air with your body partially submerged. So why won’t it work a few feet down rather than just a few inches? Simply put, our lungs are relatively weak and cannot overcome the pressure that even a foot or two of water would exert. Even just two feet down would be like trying breath with a 300 pound gorilla on your chest. It’s just not comfortable.
TUBE LENGTH
The effectiveness of a snorkel is based on a few simple principles. First, it must be the right length, basically, from the mouth to just over the top of the head. Too short and you’ll be forever inhaling water. Too long and you be fighting that gorilla on your chest or the simple difficulty of trying to move a larger volume of air through the tube. A fact that escapes many is that because not all have the same size heads, not everyone should be wearing the same size snorkel.
TUBE DIAMETER
Another variable is tube diameter, inside diameter to be specific. You would think that you’d want the largest diameter possible to make breathing easier — not so. A large diameter tube means more air to move and while this may be okay for a large diver, it could be very inefficient for the smaller diver. More “dead air” must be moved to get at the fresh air. If you are snorkeling a lot and working hard, this could make quite a difference.
TUBE SHAPE
Obviously it is not a straight shot from the top of the head to the mouth. Classic shape of the snorkel is a “J.” A modification later developed to make the shape more streamlined in the water with a curve at the top to hug the head more closely. Other effective shape modifications have followed with a slight curve to the back of the head for better horizontal snorkeling and a more effective curve at the mouth so the snorkel fits closer to the face.
For scuba divers, the most effective tube configuration is that with a flex tube in the lower portion. With this, the mouthpiece can drop away while the regulator is in use. When you choose a snorkel with a flexible lower tube, make sure that the flexible portion is still rigid enough to hold up under heavy breathing or bending (tubes that are too soft will collapse). Also, the flex tube should be smooth bore, not ridged like the exterior. A ridged interior will create breathing resistance and trap debris and water.