Of thirty-four major rivers in Florida, all except seven tributaries flow to the east or west coast. The Saint Johns River, running through Jacksonville, is the only major one to flow north. It's also the longest, traversing 273 miles to the Atlantic, as well as the most historic, for it was at its mouth that Ponce de León first landed in 1513.

Lagoons fill in the areas between barrier islands and the mainland. Some — like the Indian River, along the coast south of Cocoa Beach — while technically lagoons, flow north to south like a river.

Manatees inhabit the mouths of rivers, bays, and shallow coastal waters. They eat only aquatic plants and cannot tolerate cold conditions; they sometimes swim upriver during the winter to bask in the warm water discharged by power plants.