She's talking about Jackson Blue, which is the only spring(and the largest in the pond, one of the largest in FL infact), that has public access via a park with beach. The park is closed during the winter months, but you can obtain a key from the Sheriff's station with proof of Cave Certification.
Otherwise, you'll need to bring a boat to access the multiple springs in the Mill Pond.
You can spend the day out there diving the outside of the various caves and having fun in OW watching bream, bass, and crawfish. Access just isn't all that easy, less you have the certs or a boat.
There is a dive shop out there that rents pontoon boats.
Jackson Blue has a big cavern with a rocky bottom, but there is nothing to keep you out of the cave. Flow has been strong. Shangri La has a small cavern with a rocky bottom.
Stay out of Hole in the Wall and Twin Caves, as I hear even the caverns there are silty as hell - again, less you are cave certified.
We couldn't find Indian Washtub last time we were there, but I think its just a deeper area with a few cracks in the bottom, basically all OW. Might be fun.
We didn't have time to check out Gator Hole, but it may be worth a look.
All the above is found within the Mill Pond.