Just about each of Florida's 700-plus freshwater springs has made the claim on Ponce de León's Fountain of Youth. But we think Blue Spring State Park in Orange City—about 40 minutes from Orlando and Daytona—could possibly be "the one." We found the crystal-clear water and lush surroundings so refreshing; it's like spending the day at a natural spa.

The park is flourishing with shady live oaks, tall cypress trees and prickly cabbage palms. The bright blue spring is so inviting, you want to jump right in—and during spring and summer, when it's not manatee season, you can. Arrive early to beat the crowds and to get to know the park. To maximize your chances of seeing indigenous wildlife, opt for the peaceful, two-hour morning cruise on the St. Johns River. The pontoon boat glides past great blue herons, limpkin and the occasional alligator sunning on the riverbank. Captain Bob tells stories of cypress loggers who once used the river to transport the massive trees, and about the Army Corp of Engineers, which straightened sections of the river to make room for giant steamships.

Once you're ready to swim, the best advice is to dive in without thinking about it. Most spring-goers stand at the steps, dip their toes in the water and squeal from the chilly 72-degree temperature. Diving ensures there's an instant shock, but 20 seconds later, every nerve in your body perks up and settles into the experience.

There are two main entry points. Walk down a short boardwalk to the one closest to the springhead, formed like a large sinkhole with lush, steep banks and a popular spot for cave divers. Swim upstream; the current is constant, so you'll want to rest occasionally on a submerged log. As the sun's warm rays permeate the clear water, gar, sunfish and turtles are easy to spot, sometimes right next to you. At the springhead, look down into the majestic blue hole that eventually turns black from the absence of light. Underground pressure causes the water to bubble to the surface, creating the spring. "Blue Spring is the sole fi rst magnitude spring remaining in a natural state on the St. Johns River," says park manager Robert Rundle. It expels 101 million gallons of water a day. The water flows one-third of a mile from the springhead into the St. Johns River, which slowly crawls its way north from Melbourne's Lake Helen Blazes to Jacksonville before pouring into the Atlantic Ocean.

From Nov. 15 through March 1, the spring's main draw is the endangered West Indian manatee. The best time to view them is early morning on a cold day. Just stand along the boardwalk that lines the spring run and watch as mist rises, giving the experience a mystical feel as the sea cows lazily swim past. The animals migrate to the warm spring during the winter to escape the frigid temperature of the St. Johns River. This past January, 194 manatees were counted in a single day—a park record. Admission: $5 per car.