On the last Saturday of every month, Jim Bays slips into a pair of chest-high, brown waders and leads a small group of volunteers into Crescent Lake.
They remove garbage and floating debris and pluck out invasive species like pistia, or water lettuce.
Pistia can form a large, dense mat on the surface of the lake, choking off the elements that fish and birds need to survive. Since 2007, the Friends of Crescent Lake has removed over 200,000 pounds of the floating weed, according to Lucy Trimarco, the director of the group's steering committee.
The Friends partner with Keep Pinellas Beautiful to maintain the ecosystems at the north and south ends of the lake.
Bays, a wetlands ecologist, said they are trying to "recover and restore some measure of biological diversity."
The city once maintained the area around the lake by spraying to keep the weeds down.
Now, residents regularly see nesting birds like the limpkin, which wades through shallow waters looking for snails to eat. And they ask questions of the volunteers, trying to understand about marshes and habitats.
"If we can even make it better-looking, then the better it is for everybody," Bays said.
Keeping Crescent Lake clean has a positive effect downstream, Bays said.
Runoff from the lake flows into Coffeepot Bayou, and that feeds into Tampa Bay.