Swimming pool

• 1. Introduction

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  The swimming pool has a history that stretches back to the 3rd millennium BC, when workers at Mohenjo-Daro, in what is now Pakistan, dug a structure measuring 12 by 7 metres and sealed its bricks with tar. That pool, known today as the Great Bath, is most likely the first of its kind ever built. From that ancient beginning, human beings have never stopped building places to swim. The questions worth asking are: who built them, why did they build them, and what did those structures reveal about the societies that made them? This documentary follows the pool from its ancient origins to the record-breakers of the modern world, from the lifeguards of London's early indoor pools to the kayak-patrolling guards of a California giant so large it could not keep enough swimmers to stay open.

• 2. Ancient Origins

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  Roman emperors kept fish alongside human bathers in their private pools, which is why one Latin word for a pool was piscina. That detail, fish sharing water with the powerful, tells us something about the range of purposes these structures served from the very beginning. Ancient Greeks and Romans built artificial pools for athletic training in the palaestras, and for nautical games and military exercises. Swimming was, in those contexts, a discipline as much as a pleasure.

  The first heated swimming pool was built by Gaius Maecenas in his gardens on the Esquiline Hill of Rome, likely sometime between 38 and 8 BC. Maecenas was a wealthy imperial advisor to Augustus and considered one of the first patrons of arts. He brought warmth to the water, which was a considerable act of engineering in the ancient world.

  In Sri Lanka, ancient Sinhalese builders constructed a pair of pools called Kuttam Pokuna in the kingdom of Anuradhapura in the 6th century AD. These were no plain basins. They were decorated with flights of steps, punkalas, or pots of abundance, and scroll designs. The ornamentation signals that pools were not merely functional; they carried symbolic weight, appearing in some cases as expressions of civic pride and cultural identity.

• 3. Britain's Swimming Revival

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  As early as 1837, six indoor pools with diving boards existed in London, England, which placed Britain at the forefront of modern pool culture. By the mid-19th century, swimming pools had become genuinely popular across the country. The Maidstone Swimming Club, believed to be the oldest surviving swimming club in Britain, was formed in 1844 in Maidstone, Kent, and its founding tells a grim story.

  The club came into existence in response to concerns over drownings in the River Medway, particularly because would-be rescuers were themselves drowning when they tried to save others. Club members swam in the river itself and held races, diving competitions, and water polo matches. An 1844 report in the South East Gazette described an aquatic breakfast party where coffee and biscuits were served on a floating raft in the river, with the coffee kept hot over a fire. Members had to tread water and drink at the same time. When the last swimmers overturned the raft, 150 spectators watched with amusement.

  The Amateur Swimming Association, now known as Swim England, was founded in 1869 in England. Oxford's first major public indoor pool followed at Temple Cowley in 1939. These institutions moved swimming from an improvised outdoor activity into a structured, year-round pursuit.

• 4. Pools Go to Sea and Screen

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  The first swimming pool to go to sea was installed on the White Star Line's Adriatic in 1906. That the technology existed to bring a pool aboard an ocean liner is a measure of how seriously the early 20th century took swimming as a feature of modern life. The Racquet Club of Philadelphia clubhouse, built in 1907, boasts one of the world's first modern above-ground swimming pools, meaning the above-ground pool dates back more than a century.

  Interest in competitive swimming grew after World War I, as training standards improved and competition became more rigorous. But it was Hollywood that reshaped how ordinary Americans thought about home pools. After World War II, films such as Esther Williams' Million Dollar Mermaid turned the home swimming pool into a desirable status symbol. More than 50 years later, residential pools became a common feature of suburban life.

  New Zealand, with a population recorded at 4,116,900, holds the record for pools per capita, with 65,000 home swimming pools and 125,000 spa pools. That figure is a striking illustration of how completely pool ownership shifted from an elite luxury to a widely distributed domestic amenity.

• 5. Record Holders

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  San Alfonso del Mar in Algarrobo, Chile holds the Guinness World Record as the largest swimming pool in the world. It stretches 1,013 metres long and covers an area of 8 hectares, or about 20 acres. At its deepest point it reaches 3.5 metres. The pool was completed in December 2006.

  The Fleishhacker Pool in San Francisco was at one point the largest heated outdoor swimming pool in the United States. Opened on the 23rd of April 1925, it measured 1,000 by 150 feet. It was so large that lifeguards required kayaks to patrol it. The pool closed in 1971 due to low patronage, a reminder that scale alone does not guarantee use.

  Deep Dive Dubai, located in Dubai in the United Arab Emirates, was certified in 2021 by the Guinness Book of World Records as the world's deepest swimming pool at 60 metres. The previous record holder, the Y-40 pool at the Hotel Terme Millepini in Padua, Italy, had held the title from 2014 until 2021 with a depth of 42.15 metres.

  The highest swimming pool is believed to be in Yangbajain, Tibet, China, at an elevation of 4,200 metres above mean sea level. That resort has two indoor pools and one outdoor pool, all filled with water from hot springs.

• 6. Competition Standards

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  An Olympic-size swimming pool was first used at the 1924 Olympics. Under the additional standards set by FINA for Olympic Games and world championship events, the pool must be 50 by 25 metres wide, divided into eight lanes of 2.5 metres each, with two additional areas of 2.5 metres at each side. Depth must be at least 2 metres.

  The water must be kept between 25 and 28 degrees Celsius, and lighting must reach at least 1,500 lux. Backstroke flags are positioned exactly 5 metres from each wall. Pools that claim to be Olympic pools do not always meet these regulations, since FINA cannot police use of the term. World records are only recognized when swum in 50-metre pools, or 25-metre pools for short course events.

  A pool can be described as fast or slow depending on its physical design. Factors that reduce swimming resistance and make a pool faster include proper depth, elimination of currents, increased lane width, and energy-absorbing racing lane lines and gutters. Acoustic and hydraulic design choices also contribute. In shorter pools, swimmers gain speed from pushing off the wall after each turn, which is why times tend to be faster in shorter courses for the same distance.

• 7. Safety and Sanitation

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  A Canadian study estimated that swimmers had released 75 litres of urine into a large pool containing about 830,000 litres of water, a pool roughly a third of the size of an Olympic facility. Researchers used acesulfame potassium as the tracer to produce that estimate. Hot tubs showed even higher readings of the same marker. While urine itself is relatively harmless, its degradation products may contribute to asthma.

  Chlorine, usually added as a hypochlorite salt such as calcium hypochlorite, and bromine are the most common chemical disinfectants used to kill pathogens in pool water. Bacteria, algae, and insect larvae can breed in pool water if sanitation is not maintained. Sanitized pool water can appear green if iodine, iron salts, or copper chloride are present.

  Drowning is the most serious risk pools pose, and the risk is elevated for young children. A Centers for Disease Control article states that a majority of drownings of children between ages 1 and 4 occur in swimming pools. The American Red Cross recommends a minimum water depth of 9 feet for diving, while New York State prohibits diving in less than 8 feet. Olympic diving pools for dives from up to 10 metres must comply with World Aquatics guidelines requiring a depth of 5 metres. In regions where residential pools are common, drowning ranks as a major cause of childhood death, a statistic that underlies the pool fencing laws now enacted across many jurisdictions.

• 8. Ocean Pools and Natural Pools

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  In Australia in the early 20th century, ocean pools were built on headlands by enclosing part of the rock shelf. Water circulated through them via tidal tanks or by flooding over the sides at high tide. Many of these sites had been used for bathing by Aboriginal Australians or early European settlers before the formal pools were constructed. The pools offered protection from rough surf and sea life, and some had separate sections for men and women, or alternating access with a break in between to allow bathers to enter without being observed by members of the other sex.

  One ocean pool served as the training ground for Australian Olympian Dawn Fraser. There are currently about 100 ocean baths in New South Wales, ranging from pools roughly 25 metres long to very large facilities such as the 50 by 100 metre baths in Newcastle. The Bondi Icebergs Club pool at Bondi Beach charges a fee, while most are free.

  Natural swimming pools, developed in central and western Europe in the early and mid-1980s, take a different approach entirely. No chemicals or disinfecting devices are used; all cleaning is achieved by moving water through biological filters and plants rooted hydroponically in the system. Designers sought to recreate swimming holes and swimmable lakes, environments where people feel safe in ecologically balanced water. Natural pools can support amphibious wildlife including snails, frogs, salamanders, and small fish, and they avoid the red eyes, dried-out skin, and bleached swimsuits that come with heavily chlorinated water.