The Georgia Water Coalition on Wednesday named its annual “dirty dozen” list of the worst offenses to the state’s waters. Three of the 12 highlighted threats address water that flows directly through, under or around the Coastal Empire: the Savannah River, the Floridan aquifer and the salt marsh. Two other threats, to Georgia’s water and wetlands generally, have statewide implications but special resonance along the coast. “Savannah is kind of at the end of the line,” said Savannah Riverkeeper Tonya Bonitatibus.