The Chatham County Health Department has issued an advisory for Polk Street Beach on Tybee Island. The area affected is the northern most part of Tybee Island at the mouth of the Savannah River from the end of the beach to the jetty. The beach is not closed, but health department officials caution that contact with the water in the affected area may result in illness. The Chatham County Health Department recommends you do not swim or wade in the water in the area under advisory.