Point of Information Crossing the St. Mary's River. The St. Marys River forms part of the border between Florida and Georgia. It originates at the Okefenokee Swamp in Georgia and flows east into the Atlantic Ocean near Fort Clinch State Park. The tea-colored river features white sandbars and makes for easy paddling. Low water increases trip time considerably. This 125-mile river starts in the acid swamps of Okeefenokee and becomes a tidal river below Rt. 17 north of Jacksonville. Upstream is redbreast sunfish and small largemouth bass territory. The salt marsh zone is famous for striped bass (the same is true for nearby Nassau River). Georgia / Florida State Line to City of Ocala In Florida, “roughing it” isn’t always so rough. There are literally hundreds of great campsites throughout the Sunshine State, from deserted coastal islands ideal for tents to full-service campgrounds that can accommodate recreational vehicles.