Beyond the thrill and rejuvenating effects of city swimming, this swell of river baths challenges us to rethink how we use and abuse our urban waterways.
Cities grew up around rivers for many good practical reasons - transport, agriculture, defence, access to fresh water - and historically rivers have been at the heart of urban leisure and cultural life.
In the London of the 18th and 19th centuries, the Thames was the city's watery playground, criss-crossed with craft for transport and leisure, pomp and pageantry, frequented by swimmers as well as home to floating swimming pools.
In the 20th century, as recently as the 1950s, photos show the beaches by Tower Bridge thronged with bathers and picnickers. Today, although our waterfronts are heaving with alfresco living, beneath them is a darker underworld where few venture.
Compared to earlier centuries, we seem to recoil fearfully from urban waters. And yet the current crop of schemes for natural river and harbour baths are evidence that perhaps our attitudes to urban waterways are beginning to changing.
Reclaiming urban waterways
Harbour baths and floating swimming pools are interesting because they touch on so many aspects of the city and city living, and challenge the way we use and think about the future of our urban waterways.
Urban Plunge brings together a series of current projects for natural bathing in New York, Copenhagen, and London that offer a new water level perspective on the city.
The idea for this exhibition began to take shape about a year ago when I came across Studio Octopi's Thames Baths Project in the open call for 'London As It Could Be Now' at the Royal Academy of Arts.
The intriguing proposal for a natural bathing pool beneath the Victoria Embankment at Blackfriars struck me as a wonderful counterpoint to the terrestrial urban environment.
While the embankment streams with cars and suited people, beneath it is a place of almost surreal contrast - a pocket of watery wildness, a refuge for swimmers and wildlife right in the midst of one of the city's busiest strips.
As a self-confessed aquaholic, I began to think more about the possibilities such proposals offer for enriching urban experience.
Although there seem to be sparkling waterfront developments everywhere, these usually stop abruptly at the water's edge. We tend to treat rivers as blanks in the city waiting to be bridged or converted into boat superhighways, rather than places for people.
The result is that huge areas of our cities have effectively been cordoned off from public use, but here is evidence of a more human-centric approach.
Urban swimming from Osaka to Helsinki
Thus began a game of mentally assembling a list of like-spirited places from the Jugendstijl bathing stations on the Rhine in Basel, to the swimming channels in Zurich's Limmat, or the series of new harbour baths in Copenhagen.
I quickly identified a dozen or more new designs and proposals for urban swimming experiences from Osaka to Helsinki, from Sydney to Stockholm, from Amsterdam to Prague, London and New York. Even this morning I caught a news flash about a new floating pool for Montreal's Old Port.
Although proposals far outnumber realised baths, it seems fair to say that, as Chris Romer-Lee, architect of Thames Baths, observes: "river baths are a trending 21st century phenomenon."
Urban Plunge sets out to explore this phenomenon through a series of projects that illustrate architecture and design's role in changing river usage and challenging our attitudes to the urban water environment.
The exhibition was able materialise through the enthusiasm and support of Roca London Gallery, and our discussions around the synergies with Roca's initiatives in exploring design's role in protecting water sources through the their We Are Water Foundation.
Beyond their primary function as places to swim safely in city centres, these projects also help us to reconnect with the lifeblood of our cities.
To Copenhagen with envy
But as much as these schemes share a common spirit, what's also interesting is their different approaches.
While Thames Baths proposals for natural bathing pools at Blackfriars and Temple Stairs recall the wilderness of marshes and reed beds of pre-industrial London, + POOL's crisp design mimic's Manhattan's grid, a giant chunk of the city floating in the East River.
Conceived as an art installation, Of Soil and Water: King's Cross Pond Club explores how we can re-introduce natural cycles into the urban environment. It promises the tantalising vision of urbanites shedding their city armour to bathe in a man-made natural pond in the middle of central London's largest construction site.
In contrast Copenhagen's harbour baths are sculptural wooden promenades that create new links between land and water, social in-between spaces much like beaches.
For the moment, Londoners - apart from a rebellious few - can only dream of river swimming in the heart of the city, but if we follow Copenhagen's example that could change.
Over the past fifteen years, the Danish capital's harbour has been transformed from an industrial port to a cultural and social centre, and is now one of relatively few European cities, where it is safe to swim in the centre.
The future is blue ...
The critical step to improved water quality was modernising the sewer system and diverting wastewater that used to discharge directly into waterways during heavy rainfall.
Since the first Copenhagen Harbour Bath in 2002, a further four have opened and the phenomenally successful programme has been emulated in other Danish cities, paving the way for more ambitious thinking on urban waters.
Copenhagen's House of Water is a futuristic vision for an island dedicated to water experiences. The idea of learning about water and the environment emerged from the Danish government's Blue Plan to plant a colony of artificial islands in the capital's harbour.
House of Water's undulating white landscape looks as if an iceberg has parked up in town, and riffs on the way the geography of Nordic cities changes in winter as liquid becomes solid and sea becomes land, creating new public spaces and routes across the city.
While Copenhagen's ambitious commitment to clean up the harbour and river waters is beyond the reach of most cities at the moment, there are other approaches.
The starting point for the designers of + POOL was the realisation that if you can't clean the whole river, why not try and clean a part of it? The floating pool acts as a giant strainer filtering river water through its walls, so New Yorkers can swim in safe conditions within it.
This filtration system is currently being tested on a temporary floating lab on the Hudson River and the results published on an online dashboard so New Yorkers can track river water quality.
Will we swim in the Thames again?
It is paradoxical that while we settled around water, growing urban populations and industrialisation have turned our rivers into sewers, burying, barricading and polluting them to the point where they are no longer accessible or hospitable for human use.
Water quality, dangerous currents and increased river traffic are the arguments generally put forward against swimming in the Thames.
In her forthcoming book Downstream: a history of swimming the Thames, historian Caitlin Davies argues that a culture of fear has grown up around The Thames, we have burdened it with dangers, real and imagined, and over time this has led to the deserted foreshores we see today.
Yet in terms of water quality, the nadir was reached in the 1960s when the Thames was declared biologically dead. Since then it has improved considerably, and 'Is now the cleanest in living memory' says Davies.
Interestingly, Davies also argues that the sort of water leisure activities currently being proposed - public swims, floating baths, leisure boating - are a return to activities that used to animate urban rivers.
Seeking that 'elemental connection'
In the 19th century there were palatial floating pools at Charing Cross and Waterloo, as well as in New York and on the Seine among others. If we turned our back on urban waters through the 20th century, at last there seems to be a change in the tide.
In the case of the Thames, the Mayor of London has commissioned a feasibility study to explore if and where lidos might be positioned in the central stretch, given such issues as strong river currents, navigational routes and water quality.
Of course, the current tide of proposals for natural urban swimming is part of the larger wild swimming movement swelling in popularity in Britain and internationally.
While the lido movement in the 1930s offered sanitised swimming in chemically cleansed waters as an improvement on bathing in ponds and rivers, now we hanker after the reverse - a sense of elemental connection in our nature-deprived urban environments.
But the important point is these river and harbour baths offer a safer wild swimming experience. These river baths can be enjoyed by more than just the hardy (or perhaps foolhardy) few.
But beyond the thrill and rejuvenating effects of city swimming, this swell of river baths challenges us to rethink how we use and abuse our urban waterways, helping us reconnect to these great rivers that are all too often still treated as wastewaters in our cities.
Jane Withers is a design consultant, curator, and co-founder of Wonderwater - an initiative to develop projects raising awareness of global water issues and design for a sustainable future. Her website is at www.janewithers.com.