The main beach in Sines is a long curve of tanned sand, the sea a deep blue, a swimming area separated from the harbour with a rope line of buoys. The beach is tidy, well maintained and dotted with families. It’s the backdrop here that makes it special, the old castle dominating the skyline directly behind it and the white-washed, red-roofed old town rising up the hill toward it. I think I can see the statue of Vasco di Gamma, Portugal’s famed 16th century explorer who voyaged to India and was instrumental in opening up this trade route, beside the castle tower, a dark metal glint in the bright light. The town of Sines was his birth place.

A lot of the beaches we’ve been to here have been wild with waves, but the far out harbour walls make the water flatter. It’s still typically Atlantic cold, but not shockingly so. The wind still makes the surface pick up, spray hitting about your head if you swim into it.

I swim out to the buoys. There are few people in the water and no one by the buoys. I hang onto a seaweed-slick bit of red rubber and let it dip under my weight till I can sit on it and stare back at the beach with its tiny figures, the cliffs rising rocky to one side, the town shining in the splendour of the midday sun.

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