No Dive Guide Required.
There are only two places where it is possible to enter into the Hart Springs Cave system and Little Hart Spring is one of them. As of July 31, 2017, the only spring where it is possible for a dive to pass to enter the system is Little Hart Spring. It is at the furthermost most downstream point in the cave and flows out into a spring run which terminates into the Suwannee River. The flow is typically always very high and at times can take significant effort to enter into and progress into the cave system.
The Dive Access Qualifications page lists the requirements you must possess to dive the Hart Springs cave system. You can access that information by clicking here.
Out of the two locations, you can dive at Hart Springs, Little Hart Spring is the one location that DOES NOT require a dive guide. As long as you possess the necessary prerequisites you are welcome to visit the park and dive the cave.