Looking to pioneer a new swim in your area (or on a holiday) but not sure how to do it? You can find out a lot from an OS map. Patrick Naylor gives tips from swimmers Katie Tunn, an artist based on the Isle of Skye, and Rory Southworth, a mountain runner and wild swimmer based in the Lake District:
There is a range of OS maps depending on the activity you have in mind. The most important difference between these maps is scale, or in other words, the ratio between distance covered on paper and distance covered in the real world. Landranger Maps have a scale of 2cm to every 1km, which makes them perfect for planning holidays and long cycle routes. Road Maps have a scale of 1cm to every 2.5km, which makes them better suited to long-distance car journeys. The newest range, Urban Maps, are designed for exploring green spaces in the UK’s cities.
But most useful for discovering swim spots is the Explorer range, with a scale of 4cm to every 1km. In recent years, OS has also expanded its range of digital maps, with a user-friendly website and app which both use the Explorer model.
Scale is important because it helps you measure distances in the real world. OS has already done a lot of work for you as Explorer maps are broken down into blue boxes which each measure 1 square km. This means you can measure the distance between places and objects in a straight line. Of course, it’s rare for footpaths, country roads and rivers to follow a straight line, so you can always use a piece of string and a ruler to measure the distance of circuitous routes.
These blue boxes can also help you identify coordinates which let you mark the exact location of important features, such as car parks, access points and promising waterfalls. There are either four-figure or six-figure coordinates, depending on how precise you want to be. To work out four-figure coordinates, place your finger on the bottom left-hand corner of the blue box. First, follow this line to the top or bottom of the map (whichever is closest) and note down the number you reach. Next, follow this line to the left or right (again, go for the closest) and make a note of the number you reach. These two numbers together make up the coordinate.
If you want to be more precise, you can find the six-figure coordinate instead. Look along the edge of the map and you’ll see that each blue box can be split into 10 small sections. Fold the map over so you can see either the top or bottom, and the left or right-hand side, then follow the same process.
The OS Explorer maps are designed to help you plan routes. Contour lines can be a very useful but often much-overlooked feature. These light grey lines are drawn between points of equal height in the landscape and therefore let you determine the gradient of potential routes and the altitude of remote tarns and waterfalls. If you have an exciting new swim spot in mind, place your finger on the nearest contour line and follow this line until you find an altitude number (metres above sea level). The distance between each contour line on an Explorer map is 5m, so if you see lots of contour lines bunched together then you know there will be a steep climb.
If this sounds like too much work, OS has also embraced the possibilities of digital maps with the OS Maps website and app. A premium subscription to OS Maps includes the Aerial 3D layer which lets you “fly over” a virtual version of the landscape.
Katie Tunn and Rory Southworth both stress the importance of first deciding what sort of swimming you want to do. For example, Katie likes quiet secluded beaches, while Rory looks for deep tarns high up in the mountains, but you might also want to plunge in a river or swim between the small islands dotted around a beautiful lake.
Katie Tunn and Rory Southworth both stress the importance of first deciding what sort of swimming you want to do. For example, Katie likes quiet secluded beaches, while Rory looks for deep tarns high up in the mountains.
OS Explorer Maps include a range of symbols, such as waterfalls, marsh and reeds, nature reserves and fishing sites, which help you identify features in the landscape (or waterscape). These are published in the side panel. A single blue line represents streams, tributaries and rivers, and remember you can use contour lines to get an idea of how narrow or deep these are likely to be. A double blue line marks a river which is over 8m wide.
Most of us have stumbled across special places to swim out of pure luck, but there are also tips and tricks when searching for inspiration. Once you’ve decided what kind of swimming you want to do, Katie Tunn recommends starting off somewhere you already know before using the map to search for similar geographical features in the area. She’s found lots of secluded beaches in the Western Isles by starting with a popular beach and following the coastline to find promising new places. If you want to swim in remote waterfalls and pools, Katie also recommends looking for several waterfalls bunched together to improve your chances.
Rory Southworth recommends turning second-hand bookshops upside down to get your hands on old out-of-print books on mountain waters, before then using an Explorer map to plot routes and study the terrain. If this sounds too labour intensive, he also suggests asking your swim friends for their top five places and they might entrust you with a secret spot, perhaps in exchange for one of yours.
If you want to swim in remote waterfalls and pools, Katie also recommends looking for several waterfalls bunched together to improve your chances.
OS maps can therefore tell you a lot about possible swim spots. Roger Deakin described this process as ‘armchair swimming’ because the maps helped him create a vivid picture of the waterscape in his imagination. But there is also a lot which OS maps can’t tell you: if there’s a safe access point, the presence of submerged rocks and dangerous rip tides along the coast. In short, OS maps can get you there, but you have to decide whether it’s safe to swim.
Our Survive section is full of information on understanding water so you can work out where you (with your own abilities) are is safe to swim. Also useful, Kate Rew’s book The Outdoor Swimmers’ Handbook (available widely, and in the OSS shop).