What do the first two paragraphs describe

The first two paragraphs describe life on the island. The boys become accustomed to the pattern of their days on the island although it is impossible to adjust to the new rhythms of tropical life, which include the strange point at midday when the sea rises and appears to contain flickering images. Piggy discounts the midday illusions as mere mirages. While mornings are cool and comfortable, the afternoon sun is oppressively hot and bright, which incites fatigue among many of the boys. The northern European tradition of work, play, and food right through the day is not forgotten, making the transition difficult.

how they survived on the island when the plane crashed

What is jack doing to himself and why?