Water is the ultimate cleansing agent so its symbolism here is two-fold. Glorification has a Christian connection and water has always played a large part in Christianity. Simon was almost 'sacrificed' and ironically, the sea, a natural resource, can be both forgiving and vengeful. Water brings relief but also destruction.
Rescue will come from the sea but will not give Ralph the relief he anticipated. Things will never be the same.
Refer to the Summary and Analysis pages of enotes and navigate to Chapter 9 where you can read about and understand the significance. The writer suggests that
the great violent natural tendencies of humans are due to a flaw inherent in man’s character, a flaw planted naturally, and from which there is no civilized escape
So the glorification aspect brings a contrast to the otherwise brutal and barbaric circumstances in which the boys find themselves.
The glorification could also be interpreted as, from the boys' perspective, a cleansing for them of their wrongdoing; much like Jesus cleansing the thieves and robbers of his day - usually with water. In baptism, sins are forgiven.
Your question suggests that Golding's description, in this regard, places Simon in an exalted position, that he is deemed greater than he really is. In a religious sense, this would mean that he is, in some way, the moral superior of all others.
The description makes it clear that Simon holds a special place, to such an extent that even nature responds differently and makes his water bound burial especially significant. His death is an almost spiritual event in contrast to Piggy's later sudden and graphically brutal demise. Golding describes the event as follows:
Along the shoreward edge of the shallows the advancing clearness was full of strange, moonbeam-bodied creatures with fiery eyes. Here and there a larger pebble clung to its own air and was covered with a coat of pearls. The tide swelled in over the rain-pitted sand and smoothed everything with a layer of silver. Now it touched the first of the stains that seeped from the broken body and the creatures made a moving patch of light as they gathered at the edge. The water rose farther and dressed Simon’s coarse hair with brightness. The line of his cheek 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.
The descriptors in the paragraph all deliberately convey an event which has a surreal and extraordinarily supernatural value. It indicates a special event and its significance is emphasized by the use of phrases such as "coat of pearls," "a layer of silver," "patch of light," "brightness," "cheek silvered," and "sculptured marble." The images all convey light in the surrounding darkness, not only in a physical sense but also metaphorically, for the boys have been enveloped by the blackness of their innate evil. It is as if the reader is witnessing something holy and only realizes that the text describes an otherwise ordinary event on reading that "a bubble of air escaped from the mouth with a wet plop."
Simon's exalted state is further emphasized in the final paragraph where the journey to his final resting place is given special significance. His body is surrounded by a halo (caused by "a fringe of inquisitive bright creatures") to signify his spiritual purity and his innocence.
Simon's demise symbolizes the death of innocence. He has become the sacrificial lamb, as it were, for Man's inherent brutality. His burial, therefore, is significant, for it indicates the final incarceration of Man's innocence. This further implies that there is no going back -- Man is doomed to forever suffer from the consequences of his iniquity.