Yes, Florida's biggest water body is almost its least visible. In total Florida aquifer's hold 750 times the volume of its most conspicuous water body — Lake Okeechobee.
But Lake O is sort of invisible too: you have to climb up on the levee to see it which, when you do, looks "sea-like."
As deep as the Upper Floridan dropped, it recovered just as quickly as the freeze-thwarting pumping stopped. Areas most affected were in up peninsula near Tampa.