Crystal River

The highest concentration is in Central and North Florida, including most of the 30 “first magnitude” springs —those that discharge at least 65 million gallons of water daily. Most are considered polluted.

The lawsuit is targeting recent cuts in staff at the Crystal River National Wildlife Refuge, where reports have surfaced of manatees being harassed.

Crystal River is famous for its manatees, when hundreds flock snout to snout in the warm waters of Three Sisters Spring during winter cold snaps. But there's also a key species hiding in its waters that most people never heard of. We go on a trip to Crystal River, where two scientists are researching bull sharks.