Lenab, "bir içim su" is an idiom, but as you translated it word by word, it doesn't make sense here.
It means "Strikingly attractive, beautiful or impressive person". We can translate the first line as "You're absolutely eyeful" (or we could use an other adjective like "eyeful" )
Second line is OK.
Third line seems OK, but this would read better: "Flowers pale beside you" (="Flowers appear to be unimportant comparing with you/with your beauty" )
And the last line.. --> "I mean/It means you're very beautiful"
To sum up:
"You're absolutely eyeful
You are very beautiful
Flowers pale beside you
I mean/It means you're very beautiful"