Those who use dry snorkels are more likely to take the plunge beneath the waves to get a closer view of something. While this is perfectly acceptable to do so, there are some things that one needs to be aware of when descending to depth. The first being the effect of water pressure on the human body. While many people can understand this from a mental point of view. The pressure reference in this article is intended to encompass physical rather than mental pressure. Understanding this is better when one thinks of pressure as being the same as weight. When pressure is applied to an object it is the same as applying weight to it. How an object responds to an increase of decrease of pressure is dependent on the density of that object. The human body is under pressure every day. This is actually caused by the weight of our atmosphere. Though we don't really think about it, air does actually have weight and this weight pushes on our body constantly. The total weight at sea level is equivalent to 14.7 pounds per square inch. Since humans live is this air environment and are used to it, changes in pressure from air would have to be significant and abrupt in order to be noticeable. Water also has weight and therefore adds pressure as well. The weight of water versus the weight of air differs significantly because of the density of each. Water is 800 times denser than air which makes it much heavier.PRESSURE IN RELATIONSHIP TO SNORKELING
With dry snorkels becoming more popular, snorkelers are more apt to dive below the surface of the water in order to view something from a closer perspective. In doing so, the pressure caused by the weight of the water is going to be more change. As the depth increases so, in turn will the pressure. While many may think that this pressure will crush our bodies, it is only the air spaces of the body that are affected. These spaces include the lungs, stomach, intestines, sinus cavities and ears. To understand what this pressure change does it should be stated that when pressure is added to an air space, the molecules are compressed together. If the air space is in a flexible container the container would also compress. For snorkelers the to air spaces where the change in pressure is most noticeable are the ears and the sinuses. Anyone who has flown in an airplane or who has dove to the bottom of a swimming pool will attest to the fact that their ears are affected by these activities.EAR PRESSURE
To understand what the water pressure is doing to the ears during a descent, a little basic knowledge about the structure and workings of the ear would be helpful. The ears can be described as being divided into sections. The external ear, the middle ear and the inner ear. The external ear is what we see visually and can be easily located with one on each side of the head. This is quite useful for those who wear glasses but it's main purpose basically collects sound wave and enables them to be transmitted to the middle ear.
The middle ear is an air filled cavity which then amplifies the sound. The amplified sound is then directed to the internal ear which unlike the middle ear is a liquid filled cavity. The internal ear changes the sound waves to nerve impulses which are directed to the brain for interpretation. There is a flexible membrane that separates the external and middle ear which is called the eardrum. Since the middle ear is a cavity filled with air, it is subject to pressure changes whether caused by altitude changes or going to various depths beneath the water. The weight of the water pushes against the flexible eardrum which compresses the air space in the middle ear. In a sense it is squeezing the air much the way a person is able to squeeze a balloon. This can create an uncomfortable sensation but the human body has another unique feature which helps to alleviate this discomfort. This feature is the Eustachian tube which connects the middle ear air space to the point where the nose and mouth meet. It's purpose is to be able to equalize or regulate the air space of the middle ear. If the air space of the middle ear is compressed will allow more air into that space alleviating the inward push of the water on the eardrum. This serves to protect the eardrum from perforation.HOW TO EQUALIZE PRESSURE
Air travelers are probably the most familiar with the effect of pressure changes on the ears and the pressure changes occur on take-offs, landings and altitude changes during the flights. There are several methods that they use to equalize the pressure in their ears. Chewing gum, yawning, swallowing and holding the nose closed with the fingers and trying to blow through it. Snorkelers would be at a disadvantage with chewing gum or yawning but swallowing (called the Frenzel maneuver) or the nose-pinching method (Valsalva maneuver) are two viable means of equalization.
The Frenzel maneuver would consist of going through the act of swallowing without really swallowing. This action begins by bringing the middle portion of the tongue to the roof of the mouth in a snakelike undulation that continues toward the back of the mouth. This action usually is enough to allow air to go into the Eustachian tube and up to the middle ear.
The Valsalva maneuver would consist of the snorkeler closing off the nostrils of their nose by pinching the nose with the thumb and pointer finger of one hand. This would have to be done from the external side of the nose pocket of the viewing mask. Once closed off the next part of this maneuver is to blow air from the lungs into the nose as if trying to exhale through the nose. It must be stressed that needs to be done gently so as not to add too much pressure which would bend the eardrum outward. Many people report hearing a slight popping or even a squeaking sound when they perform this style of equalization. Those readers (you know who you are) who are trying this method right now will notice that one ear will seem to equalize before the other. The ear that will equalize first will usually have a direct relationship to whether you are right or left handed.
It has also been found that wiggling the lower jaw from side to side while performing either of the two maneuvers will also aid in the equalization process.
Whatever method proves to be effective for the snorkeler, they need to be aware that as they descend the action will need to be repeated often during the descent. Those who snorkel often may not have to do it quite as much as novices but it is important when one choose to go from snorkeling at the surface to skin diving below it.