Humans first learned to swim in prehistory – though how far back remains a matter of debate between the paleoanthropological establishment and the followers of Elaine Morgan (1920-2013), who championed the aquatic ape hypothesis, an aquatic phase during hominid evolution between 7 and 4.3 million years ago. Even though we may never have had an aquatic ancestor, compelling evidence exists for the swimming abilities of the representatives of the genus Homo since H. erectus, who appeared some 1.8 million years ago. In the historical period, the myths of the ancient civilisations of the eastern Mediterranean testify to a positive relationship with water and swimming, mediated until late antiquity by a pantheon of aquatic gods, nymphs and tritons.

By the medieval period, the majority of Western Europeans who were not involved in harvesting aquatic resources had forgotten how to swim. Swimming itself was not forgotten – but the ability to do so hugely decreased. Bodies of water became sinister ‘otherworlds’ populated by mermaids and sea monsters. How do we explain the loss of so important a skill? Humans have never given up running, jumping or climbing, so why did so many abandon an activity that was useful to obtain food and natural resources, vital to avoid drowning and pleasurable to cool down on a hot summer’s day?

The retreat from swimming began during late antiquity, as evidenced in the writings of the fifth-century Roman military writer, Vegetius, who bemoaned the fact that, unlike the hardy legionaries of the Republic, ‘whose only bath was the River Tiber’, the recruits of his day had become too used to the luxuries of the baths and had to be taught how to swim. Roman baths were furnished with large, shallow basins (piscinae), but these were designed for soaking and sitting and not swimming. Nevertheless, is it conceivable that the majority of the population of the Western Empire could forget how to swim? It is, if one considers the size of the urban bathhouse infrastructure and the concentration of the population living in inland cities in the late-imperial period. In 33 BC, Rome had 170 bathhouses; by late-fourth-century, that number had grown to 856.

Improvements in bridge and transport infrastructure and the changes in agriculture that reduced dependence on aquatic resources meant that fewer and fewer people needed to know how to swim. The swimming skills of the Germanic peoples who hastened the collapse of the Western Empire in the fifth century had impressed the Romans during their first military encounters in the Republican and early-imperial periods. Yet over the centuries, as they became Latinised and, crucially, urbanised, they adopted the Roman custom of going to the baths, until they, too, forgot how to swim.

If the growth of bathing culture provides the practical explanation for the retreat from swimming, religion explains the transformation of attitudes towards it. After the abolition of pagan cults in the fourth century, the pantheons of aquatic deities were first demonised and then quickly forgotten, breaking the positive link with water and swimming. The only survivor of this religious cull was the human-fish hybrid, the mermaid. According to Hans Christian Andersen’s The Little Mermaid (1837), mermaids were sentient but soulless, existing somewhere between humans and animals. Andersen drew on medieval traditions that portrayed mermaids as morally ambiguous beings who sometimes fell in love with and married mortal men, passing themselves off as humans, and sometimes as beguiling monsters who lured mariners to their deaths. During the Middle Ages, the mermaid symbolised an ambiguous relationship with water, especially among the mariners and fishermen of coastal communities, for whom they represented both the sea’s allure and its mortal dangers.

The French historian Jules Michelet described the Middle Ages as ‘one thousand years without a bath’. We might revise that statement to read ‘fifteen-hundred years without a swim’. The absence of bathing and swimming cultures in Western Europe predated the middle ages and outlasted them by several centuries. The elegant courtiers of 17th-century Versailles stank from lack of bathing and insanitary habits, simply because the opulent halls and apartments of the Sun King’s palace had not been furnished with bathrooms and toilets.

The only times when members of the Western European elite bathed regularly was during visits to inland spas, seeking cures for the maladies of excess. Medical bathing, though it signalled a return to the water and to a very limited amount of swimming, was not a rekindling of the positive relationship that had existed during antiquity. In some places, as in the city of Bath, the original Roman bathing infrastructure was restored, but bathers, tightly corseted in linen replicas of 17th-century fashions, complete with jaunty hats, sank and sweated rather than swam in the heated waters of the Great Bath.

The return to swimming in Western Europe was an excruciatingly slow process that began in the 16th century. Although we have no statistics for deaths by drowning in Tudor England, their number was probably greater than in the UK in the late-19th century, when between 2,264 and 3,659 people drowned annually. You might think that the only sensible countermeasure against drowning would be to teach people how to swim. But in the 1530s, German schools and universities decided that the best remedy would be a total ban on swimming, which, in the university town of Ingolstadt on the Danube, was punishable by the whipping of the drowned offender before burial. A similar ban on swimming in the Cam came into force in Cambridge in 1571, with severe punishments for infringements: two public whippings, a fine of ten shillings and a day in the stocks for a first offence and expulsion for the second.

Despite this hostile environment, several leading Tudor scholars, including royal adviser Thomas Elyot (1490-1546) and headmaster of St Paul’s Richard Mulcaster (1530-1611) recommended swimming as a form of exercise and as a means of saving lives. Most influential of all was Everard Digby (c.1550-1605), fellow of St John’s College, Cambridge, who published De arte natandi (The Art of Swimming) in 1587. A prize eccentric, Digby was expelled from the university: not for his swimming nor for his habit of jumping out on fellows and scholars loudly shouting ‘Hallo!’ and blowing a trumpet. The real reasons for his downfall were his Catholic sympathies in a Protestant-run college. Digby’s disgrace notwithstanding, updated and translated editions of his book remained the go-to text for swimming in Western Europe until the 19th century.

Like many modern swimming manuals, De arte is divided into two sections. Book I covers the theory of swimming, which Digby defines as a mechanical art whose purpose is ‘to improve health and prolong life by preventing drowning’. He referred to Julius Caesar, who, we learn in Plutarch’s Life, had escaped an Egyptian ambush on Pharos by swimming, and other heroic ancient swimmers.

Book II focuses on technique: safe entry into the water, propulsion, turning, floating, swimming underwater and diving. The text reveals Digby’s passion for swimming and his delight in amusing his friends by performing ‘decorative feats’ in the water. Digby had read ancient military and medical treatises that mentioned swimming, but in terms of its practice, as his is the earliest known formal teaching method, it is likely that he was self-taught. What makes the book particularly significant is not just the author’s modern approach to his subject matter, but also the medium of its delivery: De arte has the distinction of being the first illustrated how-to book in the English language.

The swimming breakthrough occurred in England, at the North Yorkshire coastal spa town of Scarborough in 1667, when Dr Robert Wittie recommended bathing in seawater for a wide range of ailments. The advent of medical swimming coincided with the implementation of the educational reforms proposed by Enlightenment thinkers John Locke (1632-1702) and Jean-Jacques Rousseau (1712-78) to include play and physical exercise to create a healthier and more balanced, child-centred curriculum.

Soon, the English schools public schools of Harrow and Eton were encouraging their students to learn to swim to prevent incidences of drowning, a particular concern for Eton with its rowing tradition on the Thames. The school had designated several bathing spots as early as 1727, but not all students learned to swim. The first swimming test at the school was instituted in 1836 in response to several student drownings. In the 1780s and 90s, Harrow School taught its students to swim in the ‘Duck Puddle’ – a natural pond on the grounds of the school. In 1810 or 1811 this was superseded by a second manmade Duck Puddle – a large, unlined pool that the students shared with fish, frogs and waterfowl, which was probably the first purpose-built swimming facility at an English school.

In Germany, Johann Guts Muths (1759-1839) wrote Gymnastik für die Jugend in 1793, published in English as Gymnastics for Youth in 1800, with a chapter on swimming and bathing. This was followed in 1798, by a specialist swimming book, Kleines Lehrbuch der Schwimmkunst zum Selbstunterricht (Small Study Book of the Art of Swimming for Self-study). At a time when there was little or no physical education provision in Western European schools, he wrote: ‘For my part, I consider the cold bath as an essential object in good physical education; and a bathing place, as an indispensable appendage for a public school.’ He associated bathing with swimming, thus the benefits of its practice were first, hygiene, second the saving of human life and third, exercise. Like Digby, he favoured swimming in flowing river water, but unlike his Tudor predecessor he did not allow his charges to swim naked. His students wore ‘linen drawers, reaching halfway down the thigh’ – possibly the first reference to practical male swimwear in Europe.

Guts Muths based his teaching methods on those promoted by his near contemporary, the American polymath, statesman, diplomat and accomplished swimmer, Benjamin Franklin (1706-90). According to his autobiography, Franklin learned to swim as a boy, later improving his technique by studying a French translation of Digby’s De arte natandi. In 1724 the 18-year-old Franklin moved to London to work as a typesetter. After he had succeeded in teaching two friends to swim, Franklin considered setting up a swimming school in London, thinking that he could make his fortune in a city with so many non-swimmers. Fortunately for his native country, Franklin returned to Philadelphia, but in 1726, before he left London, he gave one final demonstration of his swimming skills to several friends with whom he travelled by boat to Chelsea. Needing little encouragement, Franklin: ‘stripped and leaped into the river, and swam from near Chelsea to Blackfryar's, performing on the way many feats of activity, both upon and under water, that surpris'd and pleas'd those to whom they were novelties’.

While Franklin had performed for his friends for free, others staged swimming challenges and races for wagers and prize money. The press account of one race held in 1791 merits inclusion because of its outcome: ‘Tuesday afternoon three men, for a wager of eight guineas, swam from Westminster to London Bridge. The victor was carried on shoulders of porters to a public house in Borough, where he drank such a quantity of gin, that he expired in about half an hour after his victory.’ Gender was not a bar to taking part in such events. In 1806, a young woman swam a mile in Norwich’s River Yare ‘for a small wager’. If she swam in the female undergarments or clothing of the day, the feat is all the more impressive.

Enlightenment teachers and doctors may have led the vanguard of the swimming revival, but it was the military who initiated a systematic programme of swimming education. In Ancien Régime France, after a naval disaster had taken the lives of many naval and marine cadets who could not swim, Barthélémy Turquin opened the first École de Natation in a floating pool anchored by one of Paris’ bridges. But it was the European campaigns of Napoleon I (1769-1821) that really spurred the development of swimming. In response to repeat defeats at the hands of the French, Prussia, Austria and several major German states opened military floating pools to train both men and horses in aquatic warfare.

Humans dipped their toes in the water during the Renaissance and relearned to swim during the Enlightenment in schools, spas and barracks, but mass-participation swimming finally took off in the 19th century when the development of the railways gave millions of city dwellers access to seaside resorts and the enactment of the Baths and Washhouses Acts of 1846 and 1878 enabled English municipalities to build in-ground, heated pools in deprived urban areas.

Today, billions swim for fitness and leisure in their own or public pools and take waterside summer or winter holidays. For the growing number of wild swimmers, any body of water is a swimming opportunity. In addition to leisure, competition and health, humans swim for scientific exploration and underwater building, mining and engineering. Our dependence on swimming will only increase as we expand further into the 71 per cent of the earth’s surface covered by water. There may have never been aquatic apes in humanity’s past, but there will surely be aquatic humans in its future.

Eric Chaline is the author of Strokes of Genius: A History of Swimming (Reaktion, 2017).