Swimming on the Seine, in addition to the voluntarist political ambition to open it up to bathing that stems from the legacy of the 2024 Olympic Games, is part of a complex institutional context, structured by a series of restrictive rules laid down by the various players involved in the governance of the Ile-de-France Seine Axis: the Préfecture d'Île-de-France, Voies Navigables de France and HAROPA Port. For example, three major precautionary principles strictly govern and supervise the use of the river and condition the establishment of new bathing sites: a ban on the simultaneous cohabitation of navigation and bathing, a compulsory 5-metre setback from the river channel, and no quantitative impact on the volumes transported by freight navigation.

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A field survey carried out in 2024 (Brun, 2024) shows the extent to which these constraints have shaped the architecture and operation of the pilot sites from the outset. Naval engineering and conflicts over river sharing dictated the debates: the expertise mobilised focused on adapting to navigation conditions, rather than on the expectations or practices expected of users; and the consultation cycles conducted by the city of Paris almost exclusively mobilised river transport stakeholders and administrative managers. The debate on opening times illustrates this: on the Bras Marie site, swimming could be authorised for only half a day. At the height of summer, on a very popular tourist riverbank, a very attractive swimming area will be created, but it will be inaccessible during the hottest hours of the day.

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This paradox reveals a deeper tension: it is the management of the river as a shared space that has determined the forms of swimming, and not the other way round. From then on, swimming became an adjustment variable in a constrained space, rather than a fully assumed function of the river space. This choice was accepted from the outset by the city of Paris and the state actors involved, but may come up against the reality of use once bathing becomes popular with Parisians.

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This is why a change of scale is needed: how can we plan for the legacy of bathing in Paris so that it becomes a lasting part of the functioning of France's leading commercial river? Here we explore the need to turn to a genuine long-term metropolitan planning strategy for bathing. If the constraints in central Paris have proven too difficult to overcome, other locations offer numerous opportunities for experimentation and diversification. The Bassin de la Villette and the Canal Saint-Martin are already home to swimming sites suitable for a wide range of visitors. In the Greater Paris area, the under-utilised oxbows of the Marne and Seine rivers are protected from navigation, making it possible to bypass these conflicts of use. A case in point is the Grenelle swimming site, where the Île aux Cygnes bisects the Seine, making one of the branches safe and establishing itself as a major recreational centre. In Joinville-le-Pont, Maisons-Alfort and Neuilly-sur-Marne, urban bathing is becoming a lever for revitalising former marinas that have fallen into disrepair. In Lyon, the bathing site will not be located in the Rhône, which is too restricted by navigation, but in a protected dock in the Confluence district, allowing for lighter development and freer swimming.

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Copenhagen is a great case study, where bathing in its harbour has become the capital's flagship summer activity in just a few years. The city now has fourteen official bathing sites with a wide variety of architectural features: enclosed basins, open beaches on the harbour, integrated into the quays, etc. But it is also home to a whole network of informal bathing areas, with a wide range of facilities. But it is also home to a whole network of informal bathing sites, the result of spontaneous and free appropriation of the port areas. One of the central lessons of this research is clear: a single bath with a unique architectural typology is not enough. Each of the official port baths with enclosed basins is systematically accompanied by nearby informal bathing areas. The analysis shows that these informal bathing situations are a consequence of the development choices made: they reflect a social demand that is not met by the available supply. Certain categories of user are looking for a variety of experiences, including relaxation, spontaneity, sport and sociability, which a closed bathing area does not offer. Faced with this reality of massification and diversification of bathing uses, the response of public provision cannot be uniform. The solution found by the city of Copenhagen is therefore to offer a number of different types of infrastructure in the same area, depending on the urban fabric and the intended uses. In very busy areas, a large urban beach will channel informal practices and prevent uncontrolled bathing. On the other hand, in residential or family neighbourhoods, an enclosed pool, with more supervision, will meet ritualised family and sporting expectations.

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To date, however, the bathing facilities that are taking shape in the Paris region already seem to be limited to a single model: almost all the projects launched on the Marne or the Seine are based on closed pools. While this option seems to be favoured by local authorities for safety reasons, it excludes certain user profiles and, paradoxically, will accelerate the spread of unregulated informal bathing, in the absence of suitable solutions. We need to move away from a one-size-fits-all approach and diversify our swimming facilities now.

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There are a number of ways of doing this, including incorporating the backwaters and islands of the Seine and Marne rivers, marinas, docks and the canals of Paris (130 kilometres of which are co-managed by the local authorities in the Paris region) - all sites outside the main shipping lanes where lighter, more festive facilities could be developed: not just swimming, but also floating saunas, water sports centres and waterside restaurants. Studio Baignade Urbaine is helping the Belgian town of Mechelen, on the outskirts of Brussels, is working on a hybrid bathing site: a closed basin is combined with an open area on the canal delimited by buoys, welcoming both families and more free uses.

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These examples encourage us to think of the development of bathing facilities not as an isolated object, but as a component of a coherent territorial strategy, based on the diversity of forms and uses (Augustin & Suchet, 2016). Conflicts may have punctuated the birth of the Parisian bathing project on the Seine, but they did not hinder its momentum (Lascoumes, Timbart and Danglade, 1994). On the contrary, they gave rise to a number of innovations: greater dialogue between all the stakeholders, renewed and more appropriate governance, new navigation regulations, differentiated opening times, and adjusted sharing of uses. Opening up the Seine to bathing does not call into question Paris's role as the world's leading inland passenger port, and it goes hand in hand with the growing importance of river transport. But now a further step is needed. While the towns and cities along the Seine have taken up the challenge of making their cities suitable for bathing, they now need to develop a shared strategic vision for the city as a whole.