My first visit to the spring was a dud; although the adventure to the location was indeed fun, the spring was flooded (check the March 2010 photos for the evidence). In fact, it took me a good ten minutes to find where the boil would have been and realized that the Suwannee had flooded at least a good 4-5 feet. The sandbags on the sides of the pool were under a foot of tannic water.
I was anticipating the second visit much more but I was unfortunately let down. The lack of local interest and funding/ownership has let this spring eat itself with vegetation and overgrowth, so much so that the entire cave is covered in some kind of loosely-fitted algae and grass. I took one dive through the cave and kicked up enough of it that my camera could no longer focus on or see anything nearby. The run is nice however, and due to the relatively low crowds, some good isolated relaxation can occur.
Bottom line here is that this is as close as you will get to a spring that has good parking and good privacy. Other than that, it's not really worth much of your time.
Fanning Springs was the first stop on my five-spring day, so this visit was somewhat early in the morning (9am-10am). The spring itself was very clear and the park was mostly clean. I could have gone for a larger changing area, but that goes for basically any state park. In the morning the spring boil is under a lot of shade, which making snorkeling a little less fun. However, the way it's tucked into the surrounding wetlands with just a short walk down the floating dock to view the Suwannee, it's pretty magical in the morning. A few boats were parked at the floating dock, making it feel like a little microcosm of some of the larger springs.
While there aren't any caves that you can really get into with all the limestone rocks fallen everywhere, the sand boils are plentiful and fun to watch. The depression is also very deep, which allows for a lot of exploring. Many fish populate the spring pool, both in the weeds and out, and there's even a newly-constructed diving/jumping platform that was quite the hit while I was photographing the boil.
Overall, the park is very pristine, offers a variety of depths for swimming, lots of sand boils to watch at the bottom of the depression, and even a safe jumping platform. It can get pretty crowded, but it's one of the better swimming areas in the Florida Springs ecosystem.