I’m am blown away by the electric colour of the water. It is so so blue, an intense turquoise that feels like your eyes are playing a trick on you. I can’t believe it. You can see down to the sandy bottom where reflected sunlight dances wavy lines back and forth.

I jump in off the boat, swallowing a mouthful of salt, and swim underwater as far as I can. The visibility is incredible. The pure turquoise stretches for miles, shoals of tiny blue and silver fish darting through underwater spotlight shafts.

The rocks at the edge curve and crumble into the sea, edging the impossible blue with gold and grey and green. There’s a small beach area and we swim to it and lie on our backs letting the gentle wash of waves rock us. We explore tiny dark caves where the water shades to black and then push back out into the sunshine and the unnatural aquamarine.

Just wallowing in this water is luxurious, the colour unbelievable. It’s warm and clear and bright and even though there are lots of other people splashing in the sea, it feels incredibly special.

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