Swimming has been known since prehistoric times; the earliest record of swimming dates back to Stone Age paintings from around 7,000 years ago. Written references date from 2000 BC. Some of the earliest references include the Gilgamesh, the Iliad, the Odyssey, the Bible (Ezekiel 47:5, Acts 27:42, Isaiah 25:11), Beowulf, and other sagas. In 1538, Nikolaus Wynmann, a German professor of languages, wrote the first swimming book, The Swimmer or A Dialogue on the Art of Swimming (Der Schwimmer oder ein Zwiegespräch über die Schwimmkunst). Competitive swimming in Europe started around 1800, mostly using breaststroke. In 1873 John Arthur Trudgen introduced the trudgen to Western swimming competitions, after copying the front crawl used by Native Americans. Due to a British disregard for splashing, Trudgen employed a scissor kick instead of the front crawl's flutter kick. Swimming was part of the first modern Olympic games in 1896 in Athens. In 1902 Richard Cavill introduced the front crawl to the Western world. In 1908, the world swimming association, Fédération Internationale de Natation (FINA), was formed. Butterfly was developed in the 1930s and was at first a variant of breaststroke, until it was accepted as a separate style in 1952.


As recreation and exercise

A recreational breaststroke swimmerThe most common purposes for swimming are recreation, exercise, and athletic training. Recreational swimming is a good way to relax, while enjoying a full-body workout.

Swimming is an excellent form of exercise. Because the density of the human body is very similar to that of water, the water supports the body and less stress is therefore placed on joints and bones. Swimming is frequently used as an exercise in rehabilitation after injuries or for those with disabilities.

Resistance swimming is one form of swimming exercise. It is done either for training purposes, to hold the swimmer in place for stroke analysis, or to enable swimming in a confined space for athletic or therapeutic reasons. Resistance swimming can be done either against a stream of moving water in a swimming machine or by holding the swimmer stationary with elastic attachments.

Swimming is primarily an aerobic exercise due to the long exercise time, requiring a constant oxygen supply to the muscles, except for short sprints where the muscles work anaerobically. As with most aerobic exercise swimming is believed to reduce the harmful effects of stress. Swimming can improve posture and develop a strong lean physique, often called a "swimmer's build."


As occupation

Professional swimmers performing a water ballet in Guardalavaca, CubaSome occupations require the workers to swim. For example, abalone divers or pearl divers swim and dive to obtain an economic benefit, as do spear fishermen.

Swimming is used to rescue other swimmers in distress. In the USA, most cities and states have trained lifeguards, such as the Los Angeles City Lifeguards, deployed at pools and beaches. There are a number of specialized swimming styles especially for rescue purposes (see List of swimming styles). Such techniques are studied by lifeguards or members of the Coast Guard. The training for these techniques has also evolved into competitions such as surf lifesaving.

Swimming is also used in marine biology to observe plants and animals in their natural habitat. Other sciences use swimming, for example Konrad Lorenz swam with geese as part of his studies of animal behavior.

Swimming also has military purposes. Military swimming is usually done by special forces, such as Navy SEALS. Swimming is used to approach a location, gather intelligence, sabotage or combat, and to depart a location. This may also include airborne insertion into water or exiting a submarine while it is submerged. Due to regular exposure to large bodies of water, all recruits in the United States Navy, Marine Corps, and Coast Guard are required to complete basic swimming or water survival training.

Swimming is also a professional sport. Companies such as Speedo, TYR Sports, Arena and Nike sponsor swimmers who are at the international level. Cash awards are also given at many of the major competitions for breaking records.[citation needed]

Professional swimmers may also earn a living as entertainers, performing in water ballets.


As a competitive sport
Main article: Swimming (sport)
The aquatic sport of swimming involves competition amongst participants to be the fastest over a given distance under self propulsion. The different events include 50, 100, 200, breaststroke, backstroke and butterfly, the 50, 100, 200, 400, 800 and 1500 free and the 100, 200, and 400 Individual Medley (IM, consisting of all strokes). Swimming has been part of the modern Olympic Games since inception in 1896. Along with the other aquatic disciplines of diving, synchronised swimming and water polo, the sport is governed by the Fédération Internationale de Natation (FINA).


Styles
Main article: List of swimming styles
A style is also known as a stroke. "Stroke" can also refer to a single completion of the sequence of body movements repeated while swimming in the given style.

Several swimming styles are suitable for recreational swimming; many recreational swimmers prefer a style that keeps their head out of the water and has an underwater arm recovery. Breaststroke, side stroke, head up front crawl and dog paddle are the most common strokes utilized in recreational swimming. The out-of-water arm recovery of freestyle or butterfly gives rise to better exploitation of the difference in resistance between air and water and thus leads to higher speed.

It is possible to swim by moving only legs without arms or only arms without legs; such strokes may be used for special purposes, for training or exercise, or by amputees and paralytics.


Risks

A sign warns hikers on the trail to Hanakapiai Beach.Swimming is a healthy activity that has minimal impact on the joints. A swimmer benefits from a low risk of injury compared with many other sports. Nevertheless, there are some health risks with swimming, including the following:

Drowning, inhalation of water caused by:
Adverse water conditions swamping or overwhelming the swimmer or causing water inhalation.
Actions of others pushing the swimmer under water, either accidentally in play or intentionally.
Exhaustion or unconsciousness from various causes.
Incapacitation through shallow water blackout, heart attacks, carotid sinus syncope or stroke.
Adverse effects of immersion
Secondary drowning, where inhaled salt water creates foam in the lungs that restricts breathing.
Salt water aspiration syndrome.
Thermal shock after jumping into water can cause the heart to stop.
Exostosis is an abnormal bony overgrowth narrowing the ear canal due to frequent, long-term splashing or filling of cold water into the ear canal. (Also known as Surfer's ear.)
Exposure to chemicals
Disinfectant Chlorine will increase the pH of the water, if uncorrected the raised pH may cause eye or skin irritations. [1]
Chlorine inhalation; breathing small quantities of chlorine gas from the water surface whilst swimming for long periods of time may have an adverse effect on the lungs, particularly for asthmatics. This problem may be resolved by using a pool with better ventilation, with an outdoor pool having the best results.
Chlorine also has a negative cosmetic effect after repeated long exposure, stripping brown hair of all color, turning it very light blonde. Chlorine damages the structure of hair, turning it "frizzy." Chlorine can dissolve copper, which turns blonde hair green. Proper pool maintenance can reduce the amount of copper in the water, while wetting the hair before entering a pool can help reduce the absorption of copper.
Chlorine will often remain on skin in an anhydrous form, even after several washings. The chlorine becomes odorous once it is back in an aqueous solution (when salivated on, during a shower, etc.).
Infection
Freshwater which is stagnant, and is without chlorine treatment, is an environment which can support the survival of a wide range of bacteria, parasites, fungi and viruses, including many that can negatively affect humans. However, when a swimming pool is well-maintained, with proper water treatment to maintain good water quality, this is not the case.
Improper hygiene after walking barefoot on shower room floors and similar heavily used surfaces can allow people to become infected with the spores of the athlete's foot fungus. The easiest way to avoid this is to dry the space between the toes. [2]
Microscopic parasites such as Cryptosporidium can be resistant to chlorine, and can cause diarrheal illness when swimmers swallow pool water.
Ear canal irritation or infection known as Swimmer's ear, otitis externa, can inflame the skin which lines the ear canal. This can be very painful.
When chlorine levels are improperly balanced, severe health problems may result, such as chronic bronchitis and asthma.
Swimmer's own actions:
Overuse injury; competitive butterfly stroke swimmers for example may develop some back pain, including vertebral fractures in rare cases, and shoulder pain after long years of training, breaststroke swimmers may develop knee pain, and hip pain. Freestyle and backstroke swimmers may develop impingement syndrome, a form of tendinitis[citation needed], commonly referred to as swimmer's shoulder.
Hyperventilation in a bid to extend underwater breath-hold times lowers blood carbon dioxide resulting in suppression of the urge to breathe and consequent loss of consciousness towards the end of the dive, see shallow water blackout for the mechanism.
Adverse water and weather conditions
Currents, including tides and rivers can cause exhaustion, can pull swimmers away from safety, or pull swimmers under water.
Wind enhances waves and can blow a swimmer off course.
Hypothermia, due to cold water, can cause rapid exhaustion and unconsciousness.
Sunburn severity can be increased by reflections in the water and the lack of clothing worn during swimming. Long-term exposure to the sun contributes to risk of skin cancer.
Objects in the water
Propeller damage is a major cause of accidents, either by being run over by a boat or entanglement on climbing into a boat.
Collision with another swimmer, the pool walls, rocks or boats.
Diving into a submerged object, or the bottom, often in turbid water.
Snagging on underwater objects, particularly submerged branches or wrecks.
Stepping on sharp objects such as broken glass.
Aquatic life
Stings from jellyfish and some corals.
Piercings caused by sea urchins, zebra mussels, stingrays.
Bites from sharks and other fish and snakes, and pinches from lobsters or crabs.
Electrocution from electric rays and electric eels.
Organizations publish safety guidelines to help swimmers avoid these risks.[1][2][3]


Lessons

A Styrofoam flotation aid can help children learn to swim.Main article: Swimming lessons
Children are often given swimming lessons, which serve to develop swimming technique and confidence. Children generally do not swim independently until 4 years of age.[4]

In Sweden, Denmark, Norway and Finland, the curriculum for the fifth grade states that all children should learn how to swim as well as how to handle emergencies near water. Most commonly, children are expected to be able to swim 200 metres (220 yards) – of which at least 50 metres (55 yards) on their back – after first falling into deep water and getting their head under water. Even though about 95 percent of Swedish school children know how to swim, drowning remains the third most common cause of death among children.[5]

In both the Netherlands and Belgium swimming lessons under school time (schoolzwemmen, school swimming) are supported by the government. Most schools provide swimming lessons. There is a long tradition of swimming lessons in the Netherlands and Belgium, the Dutch translation for the breaststroke swimming style is even schoolslag (schoolstroke). The children learn a variant of the breaststroke, which is technically not entirely correct.

In many places, swimming lessons are provided by local swimming pools, both those run by the local authority and by private leisure companies. Many schools also include swimming lessons into their Physical Education curricula, provided either in the schools' own pool, or in the nearest public pool.

In the UK, the "Top-ups scheme" calls for school children who cannot swim by the age of 11 to receive intensive daily lessons. These children who have not reached Great Britain's National Curriculum standard of swimming 25 metres by the time they leave primary school will be given a half-hour lesson every day for two weeks during term-time.[6]

In Canada and Mexico there has been a call for swimming to be included in the public school curriculum.[7]