OMFG! READ THE END OF THE CHAPTER 'A VIEW TO DEATH'...it details the 'fiery eyed creatures' returning to the body and 'working round his (Simon's) head' and his body suddenly becoming buoyant (lack of head = more buoyancy) and then the pull of the moon forces the tide to come in and sweep the body away.

WOW

EDIT: I never even picked up on it the first time I read it, but it's true, they cut simon's head off...dammit!!!!! I'm going to start a band called 'decapitated Simon'