I HAVE just finished writing a book on a wildlife year on the River Devon, and for the penultimate chapter I recently donned a wetsuit, facemask, and snorkel to explore the underwater world of its estuary at Cambus.

It was a marvellous summer morning, the air still and the tide at its lowest point.

There was a short stretch of mud to negotiate before reaching the water, and I was apprehensive about how deep this glutinous ooze might be.

I waded tentatively out, but the sediment was not as soft as feared, and while it clawed at my wetsuit boots, I sunk no deeper than my ankles.

I reached an algae-covered rock shelf, pulled-on my face mask and snorkel, and plunged in.

The visibility was awful, no more than a few inches, but it was enough for me to begin to search for creatures, turning over stones with my hands as I moved slowly up the estuary.

This stone turning revealed numerous small greyish shrimp-like crustaceans called amphipods, which jerkily side-swam through the water.

These amphipods, which were up to half-an-inch long, are the engine room of the estuary, providing the food and impetus that supports so much other life, such as shelduck and teal, as well as fish.

Then, the tiniest movement on the muddy bottom, so subtle I could easily have missed it.

I looked closer and realised it was a diminutive flounder, no bigger than my thumbnail.

I turned a rock, and out scooted another small flounder, and shortly afterwards I glimpsed several more.

They would appear briefly, then bury themselves in the mud, disappearing as fast as the flick of a switch.

These flounders were an interesting discovery, and their presence highlighted the environmental importance of estuaries as places where young fish can shelter and prosper.

I also spotted tiny water snails, cased caddisfly larvae and small marine worms; the brackish water holding an eclectic mix of marine and freshwater creatures, and forming an interface between two very different environments.

On hauling myself out of the water, exhilarated at the abundance of underwater life revealed, it felt as if I had become closer to the river’s soul, experiencing its pulse and wonderful embrace.

  • Keith’s book on a wildlife year on the River Devon, ‘If Rivers Could Sing’, will be published by Tippermuir Books next month.