It is a really good question. To be honest, It misght depend on the person and the context; but, I think it is more colloquial to say "pásame el agua, por favor " o "¿me pasas el agua?" - taking into account it is the only drink on the table - when eating with family, friends, it is the same for bread, wine,sal,etc. I hope it makes sense.

If it's a formal situation you could say: ¿Podría pasarme el agua, por favor? In an informal situation: ¿Me pasas el agua?