Some do - Some DO NOT. I learned the hard way.
Look for those that actually say "For Hard Water", "For Swimmers", or those that say they are chelating. Looks for those that contain EDTA. I try to make sure even my regular shampoo has EDTA, as well.
I like Kenra Chelating. Redken has the "Cleansing Cream", but it strips my hair too much. I find the Kenra to be more gentle.
I have been trying to avoid sulfates in my shampoos and I also found ABBA Molasses clarifying that is sulfate free and good for hard water. Kind of costly, but Ebay gets me the hook up on it.
Also, I did not like that ION brand from Sally's Hard Water shampoo. Something just was not right. Makes for a decent hand soap, though.