In chapter 4, what is life like at midday?

To quote directly from the book..."Strange things happened at midday. The glittering sea rose up, moved apart in planes of blatant impossibility; the coral reef and the few, stunted palms that clung to the more elevated parts would float up into the sky, would quiver, be plucked apart, run like rain-drops on a wire or be repeated as in an odd succession of mirrors. Sometimes land loomed where there was no land and flickered out like a bubble as the children watched. Piggy discounted all this learnedly as a "mirage"...