How Copenhagen cleaned up

How the Danish capital's harbour became swimmable - plus top five spots

Bellevue Beach by Mads Eneqvist

Thirty years ago, Copenhagen harbour was polluted with industrial waste and sewage. Now writer Laura Hall doesn’t leave the house without her costume.

In 1990, Copenhagen’s harbour was a polluted industrial port, where environmental toxins mixed with human waste in the deep sludge of its darkest corners. You couldn’t see to the bottom, which was contaminated with mercury among other nasty things. Sewers emptied directly into it every time it rained, which was often. Nobody was foolish enough to swim in its grimy waters. 

These days, I don’t leave the house without a swimming costume in my bag, rolled up in a little sports towel. I’ve spent a year swimming in this harbour at least once a week, and in that time I’ve seen otters and seals, mackerel and eels, fronds of floating seaweed and legions of people swimming happily in the crystal clear water. I regularly attach a swimming camera (an Insta360) to my costume and record what I see, convinced that I’ll come back with footage of a seal’s flipper or a dance of jellyfish or the shadow of a mermaid’s tail. It doesn’t even feel that unrealistic – what does seem odd is that the harbour could have changed so much in just 30 years. 

At a time when we are thinking a lot about sewage in our swimming spaces, it’s interesting to find out that that was what kickstarted the revolution here in Denmark. Copenhagen in the 1980s was experiencing a post-industrial slump. Boat building in the city was over. Factories and shipyards were giving way to derelict spaces. Abandoned warehouses stood along the water’s edge with broken windows, like broken teeth in a freshly-punched mouth. To counteract the cycle of unending decay, the government decided to turn the ship around and create new living zones, including the one where I now live, and re-establish life under the water while they were at it.

Abandoned warehouses stood along the water’s edge with broken windows, like broken teeth in a freshly-punched mouth.

In 1992, the sewage system in Copenhagen was modernised. The next project was to work with rainwater runoff systems so the new sewage system would not be overwhelmed, and then to clean the port sediment. Water was to be carefully monitored – if you’re creating a space that is safe for people to swim in, authorities said, you have to be sure it is. So now, before I dive in, I can check on an app whether the water is clean enough. It usually is.

Kastrup Sea Bath by Mads Eneqvist

The transformation wasn’t cheap – it cost an estimated 125 million Euros to modernise the sewage system alone, and that’s going back 30 years, but the benefits for hygiene, health and daily life are clear. The blue ribbon of water that winds its way through the city, past its historic areas, along the streets lined with warehouses that have become hubs for artists and start ups and local businesses, is a playground for everyone. My apartment block, like many that border the quay, has its own kayak club so we can take kayaks and paddleboards out whenever we want. I take a harbour bus to work – an electric ferry that meanders along the water through the heart of the city twice an hour. The water is a constant feature, the lifeblood of this modern city.

Tomorrow morning I’ll be joining my friends with a very quick, very cold dip before work in a little spot in the centre of the harbour designed just for it. Cordoned off from the main boat lane in the harbour, it’s usually busy first thing in the morning, whatever the weather. Recently, with wind chill added, it’s been about -4℃ in the air and maybe 2℃ in the water. We swim with swimming costumes and woolly hats on; some people are real winter swimmers and swim in the nude. I do look forward to the coming summer, of course, when we’ll be swimming as a family in the canals near our home, at the beach, in the floating swimming pools whose nets keep the big fish out, and wherever we go. Swimming is life, once it warms up a bit. But the blast of winter cold, right to your bones, has its own charm. It makes you feel alive.

I recently saw that my old home town Bristol wants to clean up its act and that local people are campaigning to make it not illegal to swim in the harbour. I hope that they can take note of how Copenhagen has done it: making sure water is clean, sewage systems are improved and spaces are delineated so swimmers and boat goers all get to enjoy the blue space. There’s nothing like it. 

Five great swim spots in Copenhagen

Islands Brygge Havnebad

Copenhagen harbour’s premier swim spot floats beside a green space where you’ll find a great ice cream van, and comprises a couple of paddling pools for kids and families and a long laned pool for swimmers. There’s also a great stepped diving platform, beloved by local teenage boys, where you can really make a splash. Find out more

Koralbadet, Sluseholmen

My personal favourite, a quiet little floating swimming pool at the end of the electric harbour ferry line with an incredibly deep asymmetrical basin, two pools for kids and a diving platform. It’s the kind of place that can be packed on a sunny day, but when the clouds descend, you’ll have it all to yourself. Find out more

Kastrup Sea Bath

Take the metro to Amager Strandpark, the artificial beach just outside the city, and make a bee-line for this snail-shaped structure, which keeps the wind out and attracts swimmers of all types and ages all year long. It’s an award-winning piece of architecture and a lovely place to swim. You can usually see Sweden across the water on a clear day. Find out more

Svanemøllen Beach

This artificial beach is just to the north of the city centre and has lifeguards on watch and a small kiosk for snacks. Like a lot of Denmark’s beaches, it shelves slowly so you have to wade thigh deep through the clear water for a while before you can swim. But it’s clean and clear and a lovely place for a morning or evening swim. Find out more

Bellevue Beach

It doesn’t get much more Copenhagen than this: a beach outfitted with jaunty blue and white striped lifeguard towers designed by architect Arne Jacobsen. Nearby you’ll also find a petrol station/ice cream shop that he designed, called Oliver’s Garage. The beach used to be super popular but these days you can usually find a quiet spot or two. It’s always good for a photo. Find out more

Laura Hall