The St. Johns River is one of the safest and easiest gateways from the Atlantic Ocean. Between Mayport and Sanford, the river supplies an enjoyable cruise.

To Sanford, three fixed bridges set the overhead clearance at 45 feet. Snags are seldom a problem in the main channel, but you should carefully approach side streams and sloughs. Pay particularly close attention from November through March, when manatees are in residence. The current south of Palatka can be influenced by the water level in the upper (southern) part of the river as it flows south to north.

At 310 miles, it is the longest river in Florida. It is also one of the few rivers in the United States that flows north. The source of the river, or headwaters, is a large marshy area in Indian River County that flows north and turns eastward at Jacksonville to its mouth in the Atlantic Ocean.

The river’s total drop—from its source in swamps south of Melbourne to its mouth in the Atlantic near Jacksonville—is less than 30 feet, or about one inch per mile. This statistic makes the St. Johns one of the “laziest” rivers in the world. Major tributaries, or smaller streams and rivers, that flow into the St. Johns River include the Wekiva River, Econlockhatchee River, and the Ocklawaha River.

Florida waters often have a natural brown tea color caused by tannins from decaying native vegetation. Since both color and turbidity attenuate light, Secchi depth in many Florida waters is often very shallow (0.5 – 2.0 meters) compared to water bodies in other parts of the world. In Florida, this measurement is valuable for observing changes occurring within a water body over time.