The back of the beach at Deal is filled with fishing boats, hulked up out of the water, sat on shingle. The castle is low and squat and sits with a direct view of the sea. It’s that classic type of Kentish coast, where the beach stretches away in either direction for miles. You could walk on and on, from one settlement to another. It’s a bank holiday and the seafront in town is packed. A band are playing outside a pub and we walk away down the long, industrialised fishing pier. Its structure is functional, heavy set but with a brutal simplicity and the edges are decorated with jutting fishing rods. The restaurant at the end, a big glass fronted building, is closed down, deserted, but the pier is still a nice place to stare at the sea.

Back on the land we walk away from the central busy stretch of the seafront. Towels hang over striped windbreakers and a woman on a lounger flips from front to back to sunbathe. We continue past the tall pastel terraces and the rowing club till the beach gets quieter.

There’s a current in the water and I swim against it, moving only a little. The sky is fading to grey. As always, the water is deserted. There’s a boat far out on the horizon, but I’m the only swimmer I can see. I let the water, warm after months of winter, wash around me, feeling the strength with which it pushes. The shingle only extends for the first few feet from the beach, after that giving way to a softer surface, more forgiving on the feet.

Because of the current, I don’t go out far and sometimes the bottom cushions my knees. Weed tangles on my reaching fingers and I stop to free myself. The water sounds are loud when I stop, washing, splashing, slapping. I enjoy the ride and dip of the surface and how tiny I am under the sky.

I’m raising money for the Alzheimer’s Society. Please sponsor me at http://www.justgiving.com/swimbonnieswim