Sri Lankan beaches are world famous for incredible white sand and diamond clear water, but what I hadn’t realised was the toughness of the waves. At Marakolliya the pull of the water is too strong to safely swim, apart from in a kind of natural pool made by a rocky outcrop that juts out to run parallel to the beach. Even behind this, the pull is incredible. Waves break with huge force and the suck back is enough to keep you washing around in the belly of the sea. If you don’t manage to get to your feet, the water will refuse to release you.

It’s more playing and splashing and being pulled around than swimming. It’s fun and fast and a testament to the incredible, unmatchable power of the sea. We are very much its playthings. The sand is very pale and very fine, backed with palm trees. It stretches for miles, most of them deserted, with white-water fingers reaching up the shore, constantly washing in and out.

From the water, I look back. A huge wave surges and I run to pull our things back into the high grass out of the reach of the surging water. I just make it. Groups of friends mess around in the water, not just tourists but locals too, the women fully clothed. The sun is hot and it makes the sand and the water shimmer as we dry off, dress, and walk on down the beach.

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