If you’ve ever seen a wavelet break in the mouth of a burn – the tide pushing in where the stream runs out, the quick folding along a crease, the frantic ripple, a determined progress like toppling dominoes – that’s what I think of when I see the juvenile herring shoaling, not pushing through the water but unfolding, as if pulled on a line, and the sound of the fish jumping, the movement of their whole bodies, like each little splash of the wavelet.

At what seems like the edge of the world, I find a way down the rocks. The Atlantic turns over shadows where the swell lifts and a grey sky fades to nothing on the horizon. I hear an engine drop in pitch. I hadn’t noticed it until now, the drone of the motor steady above the water. All I can see from here is the boat’s dark hull and a couple of orange floats. Already it is disappearing around Boursa Island.

Kneeling on the rocks, I wonder how deep it is below me. It’s not like being on a beach where the shallows are translucent and wave froth skims the sand. Here, I can’t see beneath the chop. I imagine silt-hazy depths, currents churning. I’m scared of the sea – it’s a fear of choking, of surfacing with hair in my eyes as the next wave breaks.

A shadow, the size perhaps of an orca, sweeps through the ocean, darkness sweeping through light, then tiny ripples, the water puckering as silver rips the surface, the fish all turning over at different times. The waves jostle but where the wind whips up white flecks, the herring gleam – some arching beneath the surface and others jumping, and though I’m used to the sound of wind around this coast, this is different. The herring slap the sea as they land. Shoal Chatter.

When they come close, I see them quite clearly – each three or four inches long. One gets stranded on the rocks, flicking its body in the bladderwrack, a silver sliver on a mass of ochre weed. It convulses on its side as water washes over – water with the clarity of glass, its eye staring up at clouds and sky. Still the sea simmers as bellies flash. And again they are on the move, like iron filings following a magnet, they swirl and push, and all the time the noise goes with them.

Scotland’s Far North was the epicentre of Europe’s herring fishing in the nineteenth century. Tens of thousands of barrels were cured for export every year. I read recently that the stocks are replenishing themselves. Standing here, feeling like a character from a Neil Gunn novel, I get the sense of history, and time, being round like the world itself – a big bowl of chaos, where now and then events surface.

There is a dive site near here: an underwater wall where langoustines hide, and then a shelf, and the water-depth plunges. The fry are feeding on zooplankton – arrow worms and copepods – but I can’t help feeling that there is something in the deep chasing them. And perhaps my fear of water is that too – a fear of shadows moving below me. A fear of chaos and uncontrollable time.