Can post some picture so we know how the water marks is.
Normally, polishing or wax will remove most dirt include water marks. While water etching cause by acid rain you will need more power to remove it e.g. machine polish.
BTW, did you dry your car properly after wash? Drying is an very important step for car wash. when there is water on car paint, dust will stop on it and become water marks. Water came out from gab (e.g. side mirrir, fender) will also cause water marks. So is very important to dry it properly.