Choosing a snorkel
There are a few things to consider when choosing a snorkel. The basic plastic tubes of years gone by have been replaced by much more advanced designs that are well worth investing in. A good quality snorkel is very dry and easy to breath through, you should never need to raise your head from the water to spit out a mouthful of water.
Purge valve: A good snorkel will have a purge valve at the bottom so that if any water enters the snorkel a light exhalation will expel the water easily. Without the purge valve a snorkeler must exhale strongly to expel the water out of the top of the snorkel tube. The best purge valve designs have a chamber at the lowest part of the snorkel so that if water does enter the snorkel the water falls into the chamber and leaves the airway clear for breathing.
Wave deflector: A good snorkel will have a wave deflector on the top to help prevent a wave splashing water in to your snorkel.
Replaceable mouth piece: A snorkel should have a mouth piece that can be replaced. Usually they are attached with a cable tie. Mouthpieces are the first part of the snorkel to wear our from teeth rubbing or biting the grips. You may also want to replace the mouth piece it someone else uses your snorkel. It is also possible to buy mouth pieces that mold and set to the exact shape of your teeth. Some people find these mold-able mouth pieces reduce jaw fatigue while snorkeling. Mouth pieces should be made of silicone which is soft and will not cause mouth sores like cheap plastic will. Child sized mouth pieces can also be bought.
Snorkel shape: Lower budget snorkels are made of hard plastic and are circular in shape. They are rigid, they are not streamlined and they can break if you stand on them. Better quality snorkels are made of flexible plastic and are shaped to curve around the head. The tube is oval. All this offers a more streamlined profile when swimming through the water on the surface and underwater. Flexible snorkels can also be folded to fit in bags for transport.
The lower curved section of a snorkel can be a fixed shape or it can flex by use of soft silicone allowing it to fit in the mouth without pulling on the teeth at an angle.
Snorkel to mask attachment: Cheap snorkels are attached with a simple rubber retainer but more advanced models have clips that can be adjusted easily out of and in the water.