Tonight the river is high. I don’t know what atmospheric conditions out in the Atlantic are driving this endless rain. Like all weather these days it doesn’t seem right. My headlights project two beams across the water, which boils and writhes downstream. Nothing could swim against that. The swans are out in the fields, roosting miserably. As I drove here I glimpsed the pale fishhooks of their necks stark against the darkness. I park up, pull the key from the ignition, slam the door, and everything goes black. I can’t make out the path along the river bank for several minutes. When it appears it’s a vague line overlaying the blackness. My dog sprints ahead, her senses everywhere at once. I can hear her breathing, her footsteps on the dead leaves. I follow her slowly, trying not to trip, trying not to use the torch as my slow senses tune in. It is a few days before the winter solstice. We’re waiting for the return of the sun. Fairy lights blink in windows and doorways. Some of the houses in my village are lit up like casinos, a newish phenomenon around here. The occupants are advertising something – the bliss of an illuminated, oil-powered lifestyle. The lights remind me of aerial views of oil terminals and fracking fields, peppered with flares. Beyond the garden walls and hedges wild creatures turn away, knowing that too much light leads to blindness.

We’re given to attributing ourselves with a natural superiority over other species that allow us to do anything we like. But most of the time our superior skills and faculties are easily disproven. We are certainly not the only toolmakers, reasoners, or language users. I’ve heard it said, usually among writers, that what distinguishes humans from other species is our ability to tell stories. But this also isn’t true. The alarm call of any garden bird tells a story to other members of its community. What does distinguish humans from the rest of animal kind is our ability to make pictures. Human beings are image makers. In modern times this ability has increased exponentially and the result is that we now live inside our eyes. We channel our attention towards surfaces and contours, most often of the human face and body, represented on a flat plane – a painting, a page, a screen. These days we see more man-made images in a second than most humans in our species’ history saw in a lifetime. A film of average duration will expose us to almost 130,000 images. Over 100 million images are shared on Instagram every day. We are in desperate need of darkness. Darkness releases us from this obsession with the visual. It allows us to switch off our eyes, to disappear for a time into sounds, scents and tastes, to forget about surfaces and plunge into the depths.

It is getting late. Cloud gathers rapidly and the peak of Kilimanjaro, which has been a shining beacon since dawn, has disappeared. We’ve been following a herd of a hundred or more elephants for the past few hours. They’ve gone into thick cover and they’re hard to see, so we head back to the camp a mile away. Darkness descends like a dropped stone and tonight there are no stars. We hear hyenas for the first time, their mad cackles and growls. We glimpse their lantern eyes in the torch beam. They’re too close for comfort. A few weeks back I almost walked into a grazing hippo while going for a midnight pee and the thought of being out there tonight with hyenas about keeps me awake all night. A couple of hours after dusk I hear something brought down, the pounding of feet, a screech, the rip of skin. But for the rest of the night there is almost total silence. I wait until the sun is up before I open the tent zip. Outside, only a few inches from the guy ropes is the huge lily pad footprint of an elephant. It is one of thousands. The whole herd has passed utterly silently and invisibly through our camp in the night. The dark can even make elephants vanish.

Sometimes on a night walk you pass other walkers. You can feel the presence of people in the dark before you hear or see them. It feels like something is pushing against you, and then, as they get closer, through you. As they pass a wake is left, it takes a little more effort to balance. This sensing comes from the same part of you that feels certain places wordlessly speak. I stop for a moment where the river folds back on itself forming a grassy peninsula of a few acres edged by a stony beach. Tonight the beach is underwater, along with the boulders that form a natural weir. This is where the river speaks loudest, its voice a never repeating sequence of glottal plosives. I can just see the moving water now, a line in front of me where the darkness no longer hangs, but slides. I don’t think I’d notice anyone if they passed me tonight, the presence of the river is almost overwhelming. My dog swims at every opportunity, but tonight she’s staying back from the water’s edge. I trust her decisions. I’m not going closer. A river in flood has the same magnetic draw and repulsion as a cliff edge. You feel the line between life and death, like a strand of razor wire.

Recently the street light in front of our bedroom has been switching itself off intermittently. The faint glowing bars at the top and sides of the curtains, that give off just enough light to silhouette Julia’s face, go black and her profile disappears. I tune in to the slow, lulling rhythm of her breathing, which used to be a way to ease myself into sleep. But in the past year she’s had a cancer diagnosis and recent complications including multiple lung clots. Listening to her breathing now is no longer a relaxing experience. I lie awake waiting for signs of illness, the faint rattles and gasps that could signify some new complication. When her breaths come too slow or too fast I listen harder, and if I can’t hear her breathing I go into a flat panic.

Julia says she can picture things clearly in her mind’s eye, whole vistas filled with detail come easily to her. When I was growing up my best friend was able to draw anything, people and animals, street scenes, monsters. He seemed to be able to do this without the need for practice. Once, after heavy snow, he created a perfect image of a polar bear 30 feet across with the heel of his boot. He told me he could just see these images in front of him and all he had to do was trace the lines and fill in the blocks of tone. I could also draw pretty well, but only from an external source. When I close my eyes there’s nothing there but darkness. I’m able to describe scenes, but what I’m doing is hearing and repeating the words that describe the scene, not visualising the scene itself. My head is full of pages, usually torn from other people’s books. I think in scripts, the promissory notes of the imagination. Worse still, it’s not the words I’m obsessed with these days, but the spaces between them, which are occasionally twilit, and mostly dark. Those spaces are where the feelings are.

In this place of steep-sided hills and mountains, where for several months of the year many north facing farms never see the sun, darkness is a constant. The Welsh word Ddu means black or dark. In the Brecon Beacons there are two separate areas called Mynydd Ddu (Black Mountain), the eastern range and the smaller western range. A search for the word Ddu in a database of Welsh place names brings almost 3000 entries. There are dark fields, dark cliffs and rocks, dark lakes and streams. Many of the hills around here contain glacial lakes stranded beneath horseshoe formations – deep waters, bottomless in old stories. The most famous of these is Lyn y Fan Fach. It’s the place associated with the story of the Lady of the Lake, one of Wales’s best known legends. This is where the young shepherd saw the fairy woman walk out of the water and where she offered to become his wife if he promised never to strike her three times. And this is where, after years of happy marriage, thriving health and prosperity, she returned to the lake after he struck her for the third time, taking with her their cows and sheep, ducks and geese. They walked into the dark water in procession and were taken back to the land of the fairies, leaving the husband and sons distraught and impoverished. It’s a story about the circularity of existence, of humans and animals, and of places. Life comes out of the dark of winter. It grows and flourishes as the sun warms. Then, after three seasons, it returns to the dark.  Our ancestors believed that the soul came out of, and returned to, water. The Old Saxon word seola is derived from the proto-germanic saiwaz. Saiwa meant sea or lake. We arrive from the dark water of the womb, and at the end of life our cells liquify. We return to water, not to ashes and dust.

Almost 90% of all the water on earth exists in the total darkness of the aphotic zones. These areas are the least explored places on earth, thinly populated, as far as we know, with strange fish that can conjure their own luminescence, or navigate via electrolocation. The cave dwelling knife-fish Eigenmannia vicentespelaea produces a waveform field generated by a special electric organ. The dipole field created is shaped like a spider with circular conjoining cephalothorax and abdomen, and radiating legs. The uniform pattern changes as it comes into contact with objects having greater or lesser resistance than water. Over fifteen thousand electroreceptor cells along the length of the fish’s body then pick up these deviations, enabling the fish to navigate perfectly. Additionally it is able to adjust the frequency of its projected field if it comes into contact with another fish’s field. This is called the jamming avoidance response. Electrolocation provides these creatures with a more accurate sense than sight, they have no use for eyes. Humans have the opposite ability, we populate the darkness with what reaches out of us. The salty waters of our hearts churn like the deep convection of the Atlantic ocean causing this atrocious weather.

Two pinpoints of light hover on the mountain road then disappear and reappear, glinting between trees. The storm track that we were caught in for weeks has shifted south. There is cloud cover, no stars and the quarter moon isn’t up yet. It is not quite black, but dark enough. The water has subsided. My bare feet crunch on the beach pebbles. At the bend in the river I hear my dog go into the water, the soft plash of her entry and the half coughs of her breathing as she swims out. I’ve swum here many times but never at night. The last time I went night swimming was to clean off the dust of a week spent wild camping beneath Kilimanjaro. The air and water were body temperature, the equatorial ocean utterly still. I swam down to the reef and could see nothing at all. As I held my breath, not knowing which way was up or down, I thought that perhaps this is what death feels like. But now I believe that death has nothing to do with darkness. Perhaps it is an infinite transparency.

I step into the river.