as Ascension said, none of my players would note anything out of order - not even the rivers - although I notice those after joining the guild - thanks Ascension for adding that quirk to my repertoire

I prefer normal physics also, but if magic is in play - I'd make it really weird, like a sand ocean or an inverted waterfall - might as well go all out. For a world where other physics are at play (and damn good fantasy at that) I HIGHLY recommend Mistborn, Brandon Sanderson has made a wonderful world that works differently from ours, but is very cool ... and all is explained when the trilogi is read