Juniper Creek begins at Juniper Springs inside Ocala State Park. This river is almost unbelievably beautiful. Clear at the start - wonderful all the way through. About 5 hours.
Not for beginners - quite technical in places. It's flatwater - but hard to navigate even for an experienced tandem. If you've got skills, go for it.
Juniper Creek recreation area is on SR 40 in the middle of the Ocala National Forest.