Diving (sport)

Diving has several meanings: plunging deliberately or acrobatically into water, swimming while underwater, and using breathing apparatus such as scuba diving equipment or surface supplied diving equipment.

Humans are not the only ones to dive. Some species of amphibious animals such as marine mammals and some seabirds dive to catch their prey underwater. Equipment like submarines and remotely operated vehicles are said to dive when they descend in the water.

Sometimes the term jumping is used to disambiguate, e.g. simply for the thrill of entering the water from a high cement tower, we might say that the children jump off the tower, to describe the airborne experience, as well as the impact with the water, but not emphasizing the dive down below the surface of the water, since the intent of jumping off the cement tower is not really to dive down under the water, and in fact the depth of diving into the water is an undesirable effect that can cause barotrauma. Ideally for recreational fun, one would like to jump from a high tower, but not dive too deep after impact.

Competitive diving

When people dive in the first sense, they deliberately enter a body of water by jumping in, usually in a posture that minimises drag on entry. Arms are stretched forwards parallel to straightened legs and torso.

Competitive swimmers enter the water by diving from a set height above a specially constructed pool. Dives are performed either from springboards — long, flexible planks that bend as the divers repeatedly jump on the end of the board to gain height and speed before diving — or from rigid platforms of greater height. In elite competition, there are two springboard height competitions, at 1 metre and 3 metres; and a platform competition at 10 metres.

Such divers may perform a variety of dives, making somersaults and twists in various orientations and from different starting positions (including platform dives from an initial handstand). Divers are judged on whether they completed all aspects of the dive, the conformance of their body to the requirements of the nominated dive, and the amount of splash created by their entry to the water (less being better). The raw score is then multiplied by a difficulty factor, derived from the number of movements attempted. The diver with the highest total score after a sequence of dives (usually eight in elite competition) is declared the winner.

While not a particularly popular participant sport, diving is one of the more popular Olympic sports with spectators. Successful competitors possess many of the same characteristics as gymnasts, including strength, flexibility, and kinaesthetic judgment.

Synchronized diving was adopted as an Olympic sport in 2004. In this event, two divers form a team and attempt to perform identical dives simultaneously. This is an impressive spectacle, and requires great co-ordination between the team-mates.

Swimming underwater and diving

The ability to dive and swim underwater can be a useful emergency skill, and is an important part of watersport and navy safety training. More generally, entering water from a height is an enjoyable leisure activity, as is underwater swimming with or without breathing apparatus.

Learning to swim underwater

Assuming that you can swim on the surface, the main obstacle to diving is likely to be the psychological barrier of immersing your head. To overcome this, try hard to keep your eyes open while under the water. Don't be afraid of water getting into your eyes; although chlorinated water can sting, it is not harmful. (Salt water is less irritating.) Your eyes, nose and ears will become accustomed to immersion; plugs and goggles are advisable when there is a risk of infection, for long periods of training, or for competitive swimming.

The crucial step in gaining underwater mobility is adopting a suitable posture. To do this, first try to reach an object on the floor of the pool (or other body of water) that is within your depth. It will be difficult to reach from an upright posture. To get your hands to the object, jump up, bend your body well forward, throw your feet in the air, and try to reach the object, head foremost.

The next exercise might be to swim a few metres towards the object on the surface, and then dive for it. It is difficult at first to get the chest below the surface; but if your legs are thrown well up in the air, their weight will force your body downwards. This is surface diving (also known as a jackknife).

Swimming underwater should follow quite naturally given some practice. It is largely a matter of maintaining a slightly inverted posture so as to counteract the natural buoyancy of the lungs. Strokes used in surface swimming must be adapted somewhat, and some arm movements (such as the crawl) cannot be used.

Learning to dive into water

Diving in this sense is not as difficult as it looks; again the main barrier is psychological, as diving head-first into the surface seems likely to hurt. It does, but only if the water is entered with a large splash. Head-first tends to avoid water up the nose, but feet first often involves holding the nose. However, if going feet first, the impact often tears the arm off, losing grip, and causing water up the nose. One problem in learning, is that at first there is impact that causes bruises or pain, but once learning to be streamlined, another problem arises: pain in ears. The ear pain is often absent during initial learning because lack in coordination, etc., causes the body to land in a less streamlined way, so it does not go as deep. Once streamlined, the body goes deep, resulting in immediate and tremendous pain in the ears, from the impact and sudden increase in pressure. Ear plugs seem to mitigate such pain. For safety reasons, diving should always be done into deep water and without goggles, which can damage the eyes by way of sudden increase in pressure. Most eyewear makers, such as Speedo, include instructions that advise against jumping into water with the eyewear on. However, in competitive swimming, the swimmers seem to jump off the starting blocks while wearing eyewear, which seems to run contrary to the advice of the eyewear manufacturers.

It is best to start by entering some water where the surface is close to or level with the edge. Stoop down until you are nearly double, put your hands together over your head, lean over until they nearly touch the surface, and try to glide, rather than fall, into the water. With practise the height of entry can be increased. Next, you can try taking short run, and leaping head first into the water.

Some pools have increasing heights, 0m, 1m, 3m, 5m, and 10m, but others have only limited choices. For example, the Donald Summerville pool in Toronto has only 0m, 5m, and 10m heights available. This means that children learning must move from 0m to 5m, which is a large jump in height. At 5m, adults who are learning often climb back down after seeing the pool from the increased height, since it looks higher from above than down below. Children, however, seem to be less afraid. Children don't seem to need to wear ear plugs, or have as much problems with pain. This may be due to the volume to surface area ratio, e.g. an adult who is twice the height of a child will be eight times as heavy, but present only four times the surface area (volume varies as cube of height; surface area as square of height), resulting in deeper penetration of the water. Perhaps there is also the effect of muscles and bones having a strength that varies as the square of the length, and volume as the cube; this is why ants can fall from great heights with less damage. Therefore, it is much more difficult to learn in adulthood, if one does not learn as a child.

To make a clean entry, you should keep your body, arms, and legs quite stiff, and in a straight line. Tuck your head in so that your hands break the surface in front of it.

Feet first or head first

Head first results in more streamlined entry, and less pain, if things work out correctly, but since the body needs to change orientation 180degrees, things can go wrong, such as having legs bent, resulting in bruised thighs. The bruises that swell up usually go away after about 14 days or so. Once getting streamlined, then ears will hurt. Feet first is less streamlined, and also the nose is facing the "wrong" way, and water is blasted up the nose. To avoid this "nose enema", one hand may be used to hold the nose. Usually the hand will be pulled off, unless it is tucked in tight. Using the other arm to hold the first arm in tight helps in this regard, since the outer arm gets yanked away at time of impact, but the inner arm sometimes remains holding the nose. Crossing the legs when going feet first tends to reduce the effective impact on the genitalia, which might otherwise be felt as "referred pain" in the abdomen. When going feet first there is a choice in pointing the toes, more or less. More pointed (streamlined) impacts further up (genitalia, nose, etc.), and not pointed helps bear the brunt of the water on the feet which are often hard and caloused from walking barefoot on gravel roads.

If going head first, it is important to keep arms out to protect head. Looking down at the water will likely result in a badly bruised face, but some people take that risk and quickly pull the head in just before impact. When doing so, a common mistake is to overshoot, and to pull the head in too far, bruising the top of the head. Thus it seems easiest to keep the head steady, and also this allows the shoulders to be brought in to help protect the ears when the arms are extended. Fingers should not be interlocked, or they may be broken or damaged. Some lifeguards have suggested flat palms to bear the brunt of the water on the caloused hands, but this seems to result in more difficulty in keeping the entry streamlined and coordinated. It seems the simplest approach is keep the hands together, and the shoulders then can better protect the ears than when the hands are facing palm out.

DISCLAIMER

Please remember that Wikipedia is offered for informational use only. The information is in most cases not reviewed by professionals. You are advised to contact your doctor for health-related decisions.

Free Diving

Free diving refers to swimming underwater using only one breath of air. Depths of more than 100 meters/300 feet have been attained by world record holders. The average person may be able to reach a depth of 10 metres / 30 feet.

Snorkeling

Snorkeling is swimming at the surface with face submerged while breathing through a thin tube called a snorkel. The main aim of snorkelling is conveniently to view the underwater scenary. The snorkeller can also make short free dives from the surface.

Diving with breathing equipment

Diving, breathing equipment allows a human to remain underwater for long periods enabling recreational diving and professional diving.

Although there is a wide variety of diving equipment and techniques, to be safe and successful, each only needs to solve a limited number of common problems :

The diver must be able to breathe underwater. The two most common techniques used here are SCUBA and surface supplied diving. Standard diving dress is an historically interesting type of surface supplied diving equipment.

The diver must avoid barotrauma in the air spaces inside and surrounding the body caused by changes in pressure. This is achieved by ensuring that the pressure in all air spaces is the same as the surrounding water pressure when changing depth. This process is known as "equalising". With the air spaces in the ears, the valsalva maneouvre can be used. With the lungs, it is important breath normally and to not breath hold. With a diving mask or dry suit, air must be injected on the descent and vented on the ascent.

The diver must avoid decompression sickness. This can be prevented by decompression stops and a slow ascent using dive computers or decompression tables for guidance.

The diver must be able to see underwater. Diving masks and diving helmets solve this problem.

The diver must be able to control his or her buoyancy underwater in order to descend and ascend safely and at will. Diving weighting systems, diving suits and buoyancy compensators all contribute to the diver's buoyancy.

As water conducts heat from the diver 25 times better than air, the diver may need the thermal insulation provided by a diving suit.

Diving suits also help prevent the diver's skin being damaged by rough or sharp underwater objects and marine animals.

There are a number of techniques to increase the diver's ability dive deeper and longer:
- technical diving - use of SCUBA breathing gases other than air
- surface supplied diving - use of umbilicals and diving helmets
- saturation diving - long-term use of underwater habitats under pressure and a gradual release of pressure, over several days, in a decompression chamber at the end of a dive

The diver needs to be mobile underwater. Personal mobility is enhanced by fins worn on the feet and Diver Propulsion Vehicles. Other equipment to improve mobility includes diving bells and diving shots.

Atmospheric pressure diving suits

Atmospheric pressure diving suits solve most of the problems encountered by "ambient pressure" divers using breathing equipment, but as they are extremely heavy, cumbersome and expensive they are only used in serious professional diving.