It never ceases to amaze me how many types of snorkels there are out there, ranging from $10 going right up to the $100 range. To me this is really fascinating especially when you consider that a snorkel is in essence a simple plastic tube, one of the most basic items of diving equipment, and yet technology and design have pushed this humble device to new limits.
My most recent source of intrigue has been the Dry Snorkel. The dry snorkel and semi-dry snorkels are designed to prevent water from entering it by using a deflector device on the top. If water does get through, there is a system of purge valves that allows the water to escape before it reaches the mouth of the user. The true dry snorkel remains waterless even when your head is submerged underwater by the clever use of a float valve at the top end that seals the tube when submerged.
With one of these, a diver or snorkeler need not purge the water by blowing, thereby helping the user conserve energy on a surface swim, or while waiting for the dive boat to come pick him up. This is a big relief for those who are fed up of sharply exhaling precious air into the snorkel to clear it, at the end of a tiring dive.
There are some drawbacks of having a dry snorkel, especially for Scuba Divers, as the air filled tube can cause buoyancy, drag and even mask pull. The purge valves fitted on some of these snorkels may sometimes not fully shut, if sand or debris gets inside it, causing it to leak.
Despite the drawbacks, which seldom occur with the better quality snorkels, dry snorkels are still a remarkably efficient device that will allow you to breathe easy on those snorkeling or dive expeditions.