I learned to swim as a child in the cold North Sea at Filey, that charming resort just south of Scarborough, and swimming has been one of the greatest pleasures of my life. It is endlessly renewing. I'm not a fast, strong or bold swimmer, but I love it. I always have an eye open for a good place to bathe - a lake, a river, a beach, a brook - and long to jump into any suitable stretch of water.

I am fortunate in that I can walk in my bathing suit into the Bristol Channel from my study in the West Country, and swim towards Wales. I don't do this very often, because of the English climate and the extreme tidal pattern and the afflicting stones of the shingle shore, but the thought that I could rejoices my heart. On a warm evening, I limp over the pebbles, swim briskly for 10 minutes, then float for a while, watching the steep, wooded hills and admiring the sun as it glitters on the heather and bracken. Not many people join me. I usually have the sea to myself.

Swimming in fresh water is even more delightful. I have swum in rivers all over England. I remember a school outing near York, ostensibly to pick blackberries, when the September weather was so glorious that our little group swam naked. And I have a vivid memory of swimming with a friend in a river in Norfolk, half naked (I think we kept our pants on), to the embarrassment of our children, and finding that we were being observed by a group of village boys from a little stone bridge. The boys, unlike our children, were not shocked. They watched us, smiling, not sniggering, as though we two middle-aged women were doing the most natural thing in the world. Swimming is innocent, and that afternoon was timeless. It was as though we had stepped back into the river of the past.

Iris Murdoch and her husband, John Bayley, were great swimmers, unable to resist a dip. I met John once at a prize-judging lunch where he had to confine himself to eating scrambled eggs. He said his teeth were at the bottom of Lake Como. He'd enjoyed his bathe, he assured me, despite this misadventure. I often think of his happy smile as he told me this.

Swimming among fishes is pleasant, although it can be alarming. In Eskdale, I encountered a vast, ancient, battle-scarred salmon that swam up between my white thighs with such armoured menace that I screamed and scrambled to the bank and leaped out of the water. Little fish are not so frightening, though they sometimes nibble. Foreign fish may be more colourful, but the brown and silver and bronze-green fish of England are more subtle and graceful, and the white-starred bright green waterweeds that float in chalk streams are more beautiful to me than the exotic water hyacinths of the east.

I used to swim in Hampstead ladies' bathing pond among the bobbing moorhens and water lilies, but my favourite places now are in north Devon. There is a pool in a river in the Doone Valley, with a small rushing waterfall in which you can sit - we call it the jacuzzi. Here my daughter does brilliant imitations of Moby Dick and Salar the Salmon, aquatic displays much loved by her nieces and nephews. I sometimes go there by myself for a more spiritual immersion, but it is hard to meditate in a bracing torrent. Calmer water may be found in the enchanting Victorian sea-bathing pool at Ilfracombe. You have to time your visit carefully for this - the magic moment is when the tide comes in, in little spurts and rushes and ripples, and makes its way over the stone barriers into the safe haven of the pool. There is something uplifting about swimming on this brave incoming flow. I think of Keats each time, and of "the moving waters at their priestlike task of pure ablution round earth's human shores". Swimming with nature is good for the soul.
Margaret Drabble

Fairy Pools, Glen Brittle, Skye

The spell of the fairy pools is that they look as if they must be warm - with the kind of vivid, blue water associated with the Maldives - but, having come straight down from the Black Cuillins, they're anything but. A local swimmer warns us they're on the usual Scottish temperature range: cold, bastard cold or freezing.

We visit in late autumn, arriving from the bottom of a wide, smooth glacial basin. Suspense builds as we pass a series of aqua blue pools, each seemingly more appealing than the last. But our prize today is the two pools higher up the glen. They are separated by a rock buttress and underwater arch, so the first is choppy from current and waterfall, while the second is still. The water is so clear, every pebble and contour can be seen in its depths. Around it are rocks for jumps and dives, and flat rocks on which to sunbathe.

We climb down and undress in the warmth of the afternoon sun. There's a grass-lined cubbyhole in the cliff - just right for clothes. Perhaps it is fairy mischief that makes us abandon our wetsuits and jump into water that is face-smackingly cold. The river is at the perfect height for us to haul ourselves out on to the rock buttress and dive in again and again, then swim under the arch. This is river swimming at its most magical.

Swim Moderate. Requires some clambering in and out.

Details Park in the car park in Glenbrittle. There is a clear path up to the pools, which may need walking boots - there are streams, stepping stones and boggy bits to cross.

Llyn Idwal, Snowdonia, Gwynedd

Lakes are nature's swimming pools: safe, still bodies of water that offer tranquil swimming. The soft, green water is part of a self-cleaning ecosystem and has a life-giving quality for the swimmer as well as for fish, plants and frogs.

Lake swimming is less daunting than sea or river swimming, too. And while you may have to come to terms with a fear of the deep, there are only wind-blown waves and few currents.

There are llyns (lakes) all over Wales that are good for swimming. This one is especially good for walkers, wild campers and climbers, but the wide, stepping-stone path to it also makes it a great family option.

We start the walk up. It begins through a wrought-iron gate designed to represent the profile of the cwm (rock basin), reflected in the llyn, but conjures up an eagle's wingspan and concentric ripples on water at the same time.

Idwal is one of the best examples of a glacial valley in Wales, a wide basin in the shadow of Twll Du (known as Devil's Kitchen), with the dark cliffs and waterfall of Clogwyn y Geifr (the Cliff of the Goat) behind it. A big shingle beach looks ripe for an afternoon's picnic, playing and snoozing on a sunny day, and there's a low-lying walk right round the lake. Pictures in the visitor centre show Llyn Idwal looking eerily beautiful on misty mornings, intensely coloured in autumn sunshine.

Unexpectedly, 50 steps from the beach, it begins to pour and everything looks grey. My friend, Lulu, finds somewhere to crouch, towel at the ready, while I swim.

The only drawback of this lake for children is that it's north-facing, which, combined with its altitude, means that it's a little colder than the others. But the deep-sided cwm is stunning from the water. And minerals washed down from Devil's Kitchen would have made the grass beneath it supernaturally green, if the light hadn't been too flat to see it.

This is one of the most popular lakes in Wales (300,000 people visit each year), so tread lightly. This is the farthest south some Arctic alpine plants can survive and grazing has been excluded in different areas to allow heather to regrow.

From Idwal there is a steep climb to Llyn y Cwm (Lake of the Dog), a swim recommended by local swimmer Ross. "It's a small, beautiful lake on a popular footpath where you can easily spend an afternoon."

Swim Easy. A good lake for walkers, climbers and families.

Details Llyn Idwal is 800m long and 300m wide. There is a car park by the Cwm Idwal visitor centre (and cafe), off the A5 on the south side of Llyn Ogwen. The beach gets the sun all day in summer.

Peninnis Head, St Mary's, Isles of Scilly

There's something unreal about the Isles of Scilly, with their turquoise water and fine, white sand. The atmosphere is almost free from dust, so there are exceptionally high UV rays which, with the briny air and warm soil, encourage masses of wild flowers, out-of-season bulbs and rare mosses and lichens.

Where the west sides of the islands are exposed to the full force of the Atlantic, they are worn bare: rugged granite outcrops with only yellow gorse and purple heather for decoration. But just a mile away more sheltered bays offer safe bathing.

We scramble down a jumble of granite rocks at Peninnis Head,until we reach a dead end. We then shimmy sideways through a narrow gap and soon we're through to the most magical swimming place of all: the sea clear and blue in front of us, smooth jumping rocks all around and complete sunny, sheltered privacy from the rest of the world.

The sea is cold, clear, buoyant, fresh, and we're shivering by the time we get out, so we sit with legs and backs flat against the hot rocks, then pick up some pasties from Hugh Town and head for the St Agnes ferry.

Swim Moderate. You need to climb to get to this pool, and jump in and climb out once you're there.

Details It's impossible to give directions to this exact spot, but there are many secluded beaches and jumping spots to discover around Peninnis Head.

Durdle Door, Lulworth Cove, Dorset

If nature is your church, Durdle Door is its cathedral. Swimming under its huge arch inspires the same wonder as the Blue Mosque in Istanbul or St Paul's in London: the rock doming above us, the buoyant sea holding us aloft. You can't help but feel uplifted. The best aspect to be had is swimming out through the arch into the open sea: it feels like an adventure, a journey into boundless possibility.

The downside of Durdle Door is its popularity: it is so spectacular that it draws 200,000 visitors a year. Getting to the beach involves crossing a mobile caravan park and descending a steep, limestone path. Food choices are restricted to irradiated sandwiches and hot dogs dragged down by a tractor to a halfway point.

When we visit, the sea is tranquil, giving the water remarkable clarity, part of a stunning, white-green-blue landscape. We content ourselves with trips through the Door and around the headland, but there are also swims from the Door to the offshore rocks along the beach - the Bull, the Cow and the Calf. An even longer journey could be made to the chalk headland, Bat's Head, roughly 1km away. For those without hardy feet, aqua shoes give the option of swimming to one of these points and walking back comfortably over the pea-pebble stones.

Swim Easy to advanced.

Details Access to the beach is from Durdle Door holiday park, two miles from the A352 from Dorchester to Wareham. Durdle Door is part of the Jurassic coast, where dinosaur bones are still found. The Door itself was formed about 1,000 years ago. Take goggles so that you can see the shoals of sand eels and mackerel that shelter between the arch and the beach. You can also swim around from Man O'War Bay to the Door. The bay itself is great for swimming and snorkelling in choppier conditions, when Durdle Door seems too exposed, and is quieter and shaded later in the afternoon. Be aware of currents and tides once in the water.

Berneray beach, Berneray, North Uist

Wild swimming is an elemental thing, and places don't come much wilder or more elemental than the Outer Hebrides. In summer, cattle chill their heels in the surf; in spring, swimmers can watch eagles displaying - locking their claws and tumbling through the sky.

We wash up on North Uist in the late afternoon. The sky rolls with grey clouds and migratory birds, and the road dips between brown marsh grass and endless lochans (small lakes) - North Uist is as much water as land. We cross the causeway to Berneray for our swim. Berneray has a north-westerly beach, so today's wind is offshore. We drive through flat fields dotted with scarecrows and park the car by Highland cattle. We walk towards the dunes and are finally rewarded by a three-mile stretch of perfect white sand, the sea glinting turquoise. Clothes are off and I streak down the beach, taking in lungfuls of the clear, pure air. It's icy and gorgeous, and I dive under to feel the cold water against my eyelids. Unimpeded by clothes, the water spirals past armpits, chestbone and legs in a continual thread. It's the whole sea and me. I breaststroke parallel to the shore with the white sand beneath me, every inch of my skin fresh with cold, contentment spreading right across my frontal lobes. Then I see the grey head of a seal. I look at it and it looks at me. Then there's a splash and a spreading circle of flat water shows that it's submerged right next to me. I've been longing to swim with seals all summer. Now the moment's here and I've got no goggles or pants on. I run out of the water in faint alarm.

Later, we drive back to Uist to check out other possible swims. "Caution: otters crossing" says the sign on the causeway. We take a long, blustery walk along Traigh Ear, where an overnight storm has laid out seaweed like a natural history exhibit, then over the headland to Traigh Iar, where we earmark the in-between rocks for a future seal swim.

Swim Easy to moderate. A remote, white sand beach with few visitors. Ideal for skinny dipping.

Details Berneray beach is clearly marked on Ordnance Survey maps. For Traigh Ear and Traigh Iar beaches go to Grenitote, turn down the road marked by a phone box on the corner, follow it to the car park and walk from there. The area is known locally as Udal.

Newnham Riverbank, Club Cambridge and the Cam

An English haven. Just £16 will buy a year's membership, for the club grounds, a key to the gate and ready access to the tea and cake that are a frequent fixture on the clipped lawns. Elegant steps lead into the water, from where there is delicious swimming up to Grantchester meadows, surrounded by kingfishers and dragonflies. Privet hedges hide most of the club from the view of passing punts, allowing members to pursue their "clothing optional" policy.

As a swimming place, the Cam was made famous by poet Rupert Brooke and his band of friends dubbed the "Cambridge neo-Pagans". The group, which included EM Forster and Virginia Woolf, were agnostic freethinkers, slept outdoors and swam under the stars in a river smelling of "mint and mud".

It is not necessary to join the club because there are many swims along the Cam. Local swimmer Andrew Heather recommends the 2km stretch from Grantchester to Newnham. Keep an eye on the punts, which are often under the command of a novice. Or a drunk. Or both.

Swim Moderate. A historic 2km stretch of the Cam, great for picnics, dips or a longer swim.

Details From Grantchester Street, turn right into Grantchester Meadows. Park where this road turns into a gravel dead end and there's a small path down to the club's green wooden door. It is open all year; to join, just show up and hope there's a member to let you in.

Burgh Island, Bigbury on Sea, Devon

We're on a three-day swimming expedition in Devon and this is the finale: the circumnavigation of Burgh Island, home of an art deco hotel and many a mystery and Agatha Christie novel. We pay £1.50 to cross to the island on a sea tractor, used when the sandy spit that connects the island and mainland is cut off. We've timed our swim at the slack point of high tide to avoid currents, and the sea is flat and welcoming.

We tell the lifeguards what we're doing. "Do you want us to send a lifeboat if you're not back in an hour?" they ask. We decline; while we're all secure swimmers, we tend to dawdle and cloud-watch on pretty swims, spending time inspecting bays and floating on our backs.

The board by Burgh slipway tells us it's 14C. We put on wetsuits, booties and silicone hats, and wade in, in front of the customers at the Pilchard Inn. We turn the corner - slate rocks to our left, sea to the right. At the start of the swim we were in bucket and spade territory, with stripy windbreaks and ice cream. Now we're in sea that's properly wild.

"Once you get used to the idea that you won't get dashed against rocks, it's quite delightful," says Dom, the photographer. Walkers on the cliff top above look down as we swim between two rocks and around Cormorant Corner. The coves and cliffs that had looked forbidding now look beautiful rather than frightening. One cliff is a giant flat slab of slate, bright with reflected sun.

"We're going through that gap," I say, pointing to Death Valley, a chasm between the island and a smaller outcrop. It takes a leap of faith to swim through; waves carry you into the chasm and also push against you as you swim out. When we come out the other side, we're two-thirds of the way through our journey. We can relax now, the wild section over, but this side of the island is noticeably colder. Then we turn the final corner and get back to the beach, busy with sandcastle builders and kitesurfers.

As we step out of the water, our eyes are brighter, our smiles a little broader: our weekend has begun.

Swim Advanced. This 1.5km swim around an island takes swimmers past dramatic cliffs and unseen coves.

Details Bigbury on Sea is about three miles off the A379 from Plymouth to Dartmouth (nearest railway station, Plymouth). It is possible to get out at the beginning of this circuit, but after that you are committed. Burgh Island Hotel is a wonderful place for a cocktail or slap-up meal afterwards.

Figheldean, Wiltshire

Not far from Salisbury Plain and Stonehenge, we visit Figheldean (pronounced "filedean") on the advice of Rob Fryer, co-founder of the River and Lake Swimming Association (river-swim ming.co.uk). Pollen fluff floats lazily in the air over this small, round pool that is circled by trees and meadows. It's all shades of green: trees, grass, lilies, reeds.

It's the day for cutting river water crowfoot upstream - a controversial practice by fishery managers that creates better conditions for large numbers of fish but reduces the natural braking effect that this plant has on slow rivers. The lower pool is alive with freshly cut plants. The river is funnelled into the pool where clumps of crowfoot have a barn dance: joining hands to gallop down the centre line, then splitting left and right, and returning to the start. We step into a gap between the clumps and are charged around with them.

When we get out of the pool, we meet Reg,who has swum in here since he was a child, when he would put a tractor inner tube around a small tin bath and sat on it - "king of the castle" - while his friends tried to knock him off. His grandchildren come down now and do the same with big plastic drums.

Swim Easy to moderate. A shallow pool that offers good swimming for children.

Details Figheldean is about three miles north of Amesbury just off the A345 (nearest station: Grateley). Entering from the south, look out for the long stone wall of Figheldean House. Turn left down the cul-de-sac opposite.

Blue Lagoon, Abereiddy, Pembrokeshire

It's the jumping that people most come to the Blue Lagoon for. There's a nice beach, and great scuba diving, but it's the chance to hurtle off the blackened walls of an old quarry into clear, deep blue water that draws the crowds.

We are the first people to arrive after a morning storm. The sea is still full of whitecaps but the lagoon, protected by steep cliffs, is flat and calm. Standing on the lowest wall, a South African teaches me to jump "properly". "Cross your arms over your chest and keep your feet together. Don't hold your nose - you might break it when you land."

Duly instructed I plunge off the baby wall, which feels high to me. The walls are between 20 and 45 feet above the water. The South African hurtles off the top in a running leap, clearing six feet of wall before leg-pedalling out into the water. Afterwards we swim out of the channel that connects the lagoon to the sea, and around on to the beach, for huge cups of chai.

Swim Easy, popular with families.

Details Abereiddy can be reached by following signs from Croesgoch on the A487 (St David's to Fishguard road). Divers and swimmers may see seals, corals, anemones and spider crabs.

Porthtowan tidal pool, Cornwall

The north coast of Cornwall is dotted with sea pools that give swimmers a chance to bathe safely, away from the big waves so popular with surfers. This looks like a place where mermaids would swim: purple, turquoise and bright green seaweeds cover the bottom. I suss out the rocks, then stand on a ledge by the sea wall. Hundreds of gallons of water are smashed into the air as the waves are broken by the wall. My heart pounds as I swim around the pool, but I am soon waiting for the next wave. It's hard to imagine any wild pool beating this swimming experience.

Swim Easy. Wild and exhilarating.

Details Porthtowan is about four miles north of Redruth. There's a chain of tidal pools along this coast: Portreath, Lady Basset's Baths (also Portreath), Millendreath, Polperro and Treyarnon Bay.

Lumb Falls, near Hebden Bridge, West Yorkshire

Until heated swimming pools came along in the 50s, everyone learned to swim outdoors. There are traditional bathing spots, where you can join in the splash and chat of children and picnickers, and remote crags known only to climbers and ramblers.

If you want to know where to swim, ask local teenagers - I found this place through MySpace, where some were arranging to meet. We reach the falls down a footpath, past damp, stone walls, morning dew and sheep grazing on a cabbage field. Signs of popularity are there: a fallen tree is scuffed smooth by boots, and next to it lies ash from a campfire.

Beneath the falls is a small, semicircular pool overhung by ferns. We get in and there's a mossy cliff that leads up to a rock ledge. I'm not great at heights, but the constant roar of the falls somehow drowns out normal thought, and I can't hear my own vertigo, so I climb up.

It turns out to be a good ledge for jumpers and non-jumpers alike - high enough to be thrilling, not so high that it's terrifying. Always check water depth before jumping. This pool can be shallow; when we visited previous swimmers had dammed it up to keep it deep.

Swim Easy, but some scrambling is required to get to the falls.

Details You will need an Ordnance Survey map to locate this pool on a footpath between Shackleton Moor and Hardcastle Crags.

Wild Swim: River, Lake, Lido & Sea by Kate Rew is available for £9.99 (RRP £12.99) with free UK p&p from the Guardian Bookshop.