Heading out of St Ives, we walk up and along the rocky headland. Far below us perfect secluded crescents of white sand lie tantalisingly close. One looks accessible, but when we get a bit closer it’s clear the way down is too much of a scramble to be safe, so we reluctantly retreat back to one of the town’s main bays, Porthmeor.

Sticking to one end of it, we find the water is empty and the sand is sticky and interspersed with saltwater pools. We stack our clothes high on a barnacle encrusted rock and go in.

The sun dances between cloud and clear sky, highlighting the edges of the waves and then dropping them into shadow. The waves, spaced far enough apart to swim or recover in between, are white tipped and rising. Usually, I jump them, kicking off as they approach and riding with them, head above water, face turning from the spray. But today I discover the heady joy of diving through them. Goggles making all the difference, I approach each oncoming rush with anticipation before plunging through, arms stretched into a point before me, to watch the water tumble, to see the sand patterns dance below me. I feel like a child and a sea creature.

Turning the other way, I body surf for spurts toward the beach, letting my weight be carried as I look down through clear water rapidly decreasing in depth. We play till a couple come in beside us. By then the sun has dropped and we are hungry and ready to dry in what is left of the sun. I feel like I’ve discovered a whole new experience, one which was there and available to me all along.

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