Visitors from drier climates are sometimes shocked to see how huge the rivers can get in coastal Georgia and South Carolina, how wide and voluminous as they saunter to the sea, their seemingly slow speed belying the massive power they contain. Georgia and South Carolina’s big alluvial, or sediment-bearing, rivers originate in the region of the Appalachian mountain chain. The headwaters of the Savannah River, for example, are near Tallulah Gorge in extreme north Georgia.

Some rivers form out of the confluence of smaller rivers, such as Georgia’s mighty Altamaha, actually the child of the Ocmulgee and Oconee Rivers in the middle of the state. Others, like the Ashley and Cooper Rivers in South Carolina, originate much closer to the coast in the Piedmont.

The blackwater river is a particularly interesting Southern phenomenon, duplicated elsewhere only in South America and one example each in New York and Michigan. While alluvial rivers generally originate in highlands and carry with them a large amount of sediment, blackwater rivers originate in low-lying areas and move slowly toward the sea, carrying with them very little sediment.

Rather, their dark tea color comes from the tannic acid of decaying vegetation all along their banks, washed out by the slow, inexorable movement of the river toward the sea. While I don’t necessarily recommend drinking it, despite its dirty color “blackwater” is for the most part remarkably clean and hygienic.

Blackwater courses featured prominently in this guide are the Edisto River (the longest blackwater river in the world), Ebenezer Creek near Savannah, and Georgia’s Suwannee River, which originates in the Okefenokee Swamp and empties in the Gulf of Mexico. Georgia’s Altamaha River is a hybrid of sorts because it is partially fed by the blackwater Ohoopee River.