please help with my water stain

 have beautiful uba tuba granite countertops in the kitchen.  One of my countertops has a nasty water ring mark on it.  I have sealer that I bought at our local home depot  which I am not loving.  Is there any way to remove this water spot and can you recommend a good sealer.  Also, how often should sealing be done (counters are 5 years old).  Thanks.

Cindy Follman