How does the description of Simon's dead body being washed away to sea suggest his apotheosis?the combination of descriptions of the creatures, Simon's body, the sky, and the water.
Golding's use of light imagery in this scene leads to a tone of gentleness. He describes how the water "dressed Simon's coarse hair with brightness" and the "moving patch of light" made by the phosphorescent creatures. Then Simon's body essentially becomes art:
The line of his cheeks silvered and the turn of his shoulder became sculptured marble. The strange attendant creatures, with their fiery eyes and trailing vapors, busied themselves round his head. The body lifted a fraction of an inch from the sand and a bubble of air escaped from the mouth with a wet plop. Then it turned gently in the water.
Some have suggested that this is Christ imagery as well. whether or not you agree with that, there's definitely a sense of Simon becoming more than a dead body. He is lit up by the "strangely attendant" creatures, implying that they recognize he should be taken care of in some way. Also, the movement in the water may suggest a transcendence of death.
A person undergoes an apotheosis when they are exalted to the point of becoming like a god. So what we are looking for is things that show that Simon is being compared to a god or something equally exalted.
We see this with Simon because it seems like the whole world, or at least the sea and the sky and the creatures of the sea are working together to remake him. We see Simon being "dressed with brightness" and him being made into marble. He becomes a silver shape, attended by creatures (angels?), moving out to sea.