Ok, I got fed-up saying that I was confused by Pagan symbolism.
"No one who is conversant with the way in which men's minds operated in the Middle Ages ought to find any difficulty in thinking of the Grail as a Christianization of a heathen vessel of plenty." (Brown)
This fits in with the place where the grail first appeared (in Chretien's version, p. 420) because it was in a feast hall, carried by a young woman who was accompanied by two young men. Youth and plentiful food might suggest abundance and fertility. Also interesting is that Pagan religions, such as Wicca, often think of their deity, or the Earth, as a Goddess. Maybe it is and maybe it is not a coincidence that it was a girl who carried the grail?
Also, according to the websites listed below which are about modern Pagan religions, water is also a symbol of fertility. Perceval's path changed when he came to the river and met the Fisher King (418). A symbols of the element of water (also according to the aforementioned websites) are chalices, goblets, cauldrons, cups, pitchers, and very likely these include something that could be a grail.
Brown also makes a case that the mentioning of fish in relation to the grail (Chretien 460, also thematically) might actually suggest an accident in the translation due to the fact that the Irish/Gaelic word for "fish" is spelled very like the word for "host" in French. He says that instead of the Fisher King living off of a single host served from the grail perhaps he lives off of some kind of fish (footnote 1, p. 402).
Brown, Arthur C. L. "From Cauldron of Plenty to Grail" Modern Philology, Vol. 14, No. 7. (Nov., 1916), pp. 385-404.link from JSTOR if you are at an on-site location.
This is a JSTOR article that I'm having trouble getting a link from. If I take the link they ask me to then when I click on it they tell me I have to be on campus! The other one should work, but I'm not sure if you have to be logged in or not. Use the keywords of the title and author to find it if you can't get to it from a link. Brown is a bit opinionated and the article does assume that you have a working knowledge of French and Latin, which I don't. It is neat to see how Chretien rhymes, though.
Spring Wolf. "The Alchemy of Life" Spring Wolf's Spiritual Education Network: The Pagan's Path" 1997-2004. last visited: 09-16-04. link
"Element Water" Pagan at Osn. last visited: 09-16-04. link
"Correspondences: Element of Water" PaganNews.com last visited: 09-16.04. link
Devorah. "Magickal Symbolism: Elements and Directions" Music for the Goddess last visited: 09-16-04. link
n.b. regarding the websites: These were not hard to find through Google.com but I should have taken a lengthier search on one of our college's databases to come up with possibly more reliable information.