seeing shadows / lights, deja vu, and the feeling of 'seeing something' before it happens are all dehydration related. your brain acts weird when it doesnt have the resources to go the pathway it wants to use. gets even weirder when you sleep while dehydrated and is linked to insomnia and believing the events of a dream are real, and even more weirder when you consider daydreams

and then of course when you consider most gungho religions started in the middle east, a very hot place...