Anyone have any tips? Last owner must have had this car parked next to sprinklers for years . . .

 

Rubbing compound, if it's bad enough you may need to wet sand and worse case scenario is you just can't get it out at all without a repaint. ( probably the case )

 

A water spot would be a ring of dust left on the paint after a bead of water has dried. That can be wiped with rag, rubbed with microfiber cloth and rubbing compound.......rewashed and chamois'd..............whatever.

If its not a water spot (damage on the paint) thats another story

 

If its covering a good amount car go down to NAPA and buy a bottle of 3M liquid rubbing compound for about $14. Fantastic product! Works great for getting wet sand swirls out of new/old paint and shines it enough to look great. I would recommend you buy a good quality cleaner wax too such as Zymol. Don't cheap out and buy cheap wax products. It is worth the money.

 

Although it could be chemicals that ate away at the paint... Carb cleaner, brake cleaner, brake/clutch fluid.