CHIEFLAND, Fla. — To the untrained eye, Manatee Springs is an idyllic refuge in Central Florida: The cool water is so clear in parts that the sand glistens like polished aluminum. A vast series of underwater caves beckons thousands of divers. Deer wander by as do manatees, turtles, owls. Eagles soar overhead.

But Annette and Mark Long, who live a stroll away from the cypress-filled park, know differently. The natural springs here are ailing, as are many of the 900 other springs in the state. For decades, fertilizer and cow manure from nearby dairy farms have seeped into the porous ground at Manatee Springs and by extension the aquifer, which supplies most of the state’s drinking water, scientists said. The nitrates from the fertilizer have bubbled up into the springs, killing off eelgrass and fish, and raising toxicity levels.

Today, Manatee Springs is one of the most polluted springs in the state.

“The algae floats in clumps,” said Mrs. Long, president of the environmental group Save Our Suwannee, pointing to patches near where a few swimmers braved the icy waters. “Those dark splotches are just algae sitting there. The pollution grows so fast it kills most everything else.”

After years of discussion and inaction, four influential Republican State Senate committee chairmen and one Democratic chairman have signed off on an ambitious bill that would lay the groundwork for a long-term, comprehensive approach to restoring the state’s 38 most important and threatened springs. But the proposal, which has a price tag of $380 million for next year, requires concessions from agriculture, home builders, septic tank owners, property rights advocates and other powerful interests. And the measure poses a difficult test of whether divided Republican legislators have the will to address the problems in a comprehensive way.