The paddle upstream to the spring (4 miles) can easily be stretched to 5 hours or abbreviated to 2. Dawdle to watch for birds and otters. There are also many alligators, ibis, sparrows, great blue herons, little blue herons, bees, and butterflies. The butterflies really put on a show. There are many, many anhingas and cormorants including a nesting colony near the spring. There is a large colony of monkeys in this area and they will often show themselves for boaters, likely because they have been fed by humans. They are so cute. Rumor is, they will jump onto boats and steal food. Maybe.
The spring source is Silver Springs, a private recreation area. Paddling over the spring is permitted however boaters may not disembark. Statues can be seen in the spring, the film site for several movies including "Tarzan". The view is very dramatic, a unique experience for paddlers.
The Silver River is astoundingly beautiful. The water is a deep azure color. The river is 30 feet deep in places. Very large fish (gars and catfish) can be seen in the water as well as many turtles. Many of the plants are in bloom. A few spots are suitable for swimming. Motorized craft are permitted, however, it is a no wake zone. The return trip is easy, downstream, and could be completed in 100 minutes or less with a little effort.
If you go, be sure to take plenty of water, snacks, sunscreen, personal flotation device, whistle, water shoes, and an extra paddle. Watch for larger boats. This is not a paddle for beginners or non swimmers, however I would rate it as easy. Maps are not needed.