There is a particular kind of swimming that has nothing to do with lanes, lap counters, or chlorine. It happens at the edge of things - where land meets ocean, where rock has been shaped by tide and time, where the water is cold and alive and connected to something much larger than a pool. It happens in places that were carved by volcanoes, built by hand during the Depression, or simply discovered one afternoon at the end of a rocky path.

They exist on almost every coastline in the world, and no two are alike. Some are grand civic monuments, art deco curves cut against a crashing surf. Some are nothing more than a hollow in the lava, filled twice a day by the Atlantic. Some are free, some are heritage listed, some require a scramble down a cliff to reach. What they share is harder to define - a quality of place, of wildness held just barely in check, of swimming that feels like it actually means something.

This is a celebration of the best of them. From the sun-bleached rock pools of Australia to the volcanic coastlines of Iceland and Madeira, from the lidos of Cornwall to a hidden lagoon on a Greek island most people haven't heard of - these are the pools worth travelling for. Bring a towel. The water's cold. Get in anyway!