A sail from Charleston to Jacksonville is a matter of crossing 11 sounds, the rivers that connect them and in some cases land cuts that were dug to connect the rivers. Below is Henry Plummer's hand-drawn map of the sounds from THE BOY, ME AND THE CAT, CRUISE OF THE MASCOT, 1912-1913. He shows, from north to south, St. Helena, Port Royal, Ossabow, St. Catherine, Sapelo, Doboy, Altamaha, St. Simon, St. Andrews, Cumberland and Nassau Sounds.
I've been sailing sounds for years: Pamlico, Albemarle and Tangier. Below is a photographer from 2014 on my first crossing of Pamlico Sound from the mainland to Ocracoke, about 16 miles. Weather was fair that day. A year or two later I crossed from Ocracoke to the mainland under small craft warnings, very pleased with the yawl's ability to sail under just mizzen and jib.
It is interesting to me that the sounds of South Carolina and George are much narrower bodies of water than what I am used to. Most are two or three miles. The narrowest, Buttermilk Sound, not shown on Plummer's map, is just a quarter mile wide. With the amount of water that drains through the sounds I do expect there will be stronger tides than those found in North Carolina and Chesapeake Bay.
The map also gives some time frames worth referencing. Plummer sailed MASCOT, a 24 ft. 6 in. long catboat. The boat had no engine but they towed a small powered "push boat" for when there was no wind. On the passage south they are in Charleston on January 9, reaching the Jacksonville area on January 28. Nineteen days. North bound they are in the Jacksonville area on March 23, reaching Charles on April 13. Again, nineteen days. Sounds reasonable.