CRYSTAL RIVER -- Lee-Anne Biederman slipped quietly from her dive boat into the cool, 71-degree water of King’s Bay, hoping to encounter some of the 400-600 endangered manatees that stop here each winter. A Canadian transplant to Austin, Texas and a self-described animal lover, she had never been up close with one of the gentle marine mammals before.

Biederman was not disappointed; a manatee followed her as she snorkeled the shallow waters. Another pulled her hair and a third, a young manatee, swam up to kiss her dive mask.

“Amazing!” she gushed on the boat ride back to the dive shop at the Plantation at Crystal River. “It was pretty cool.”

Biederman is among more than 100,000 visitors from around the globe expected in the small west-Florida city of Crystal River this year for the express purpose of encountering manatees. More than 114,000 people swam with the creatures last year, up from 93,000 in 2011.

Crystal River, located 10 miles inland from the Gulf of Mexico and fed by numerous freshwater springs large and small, is unique. According to Ivan Vicente, a veteran ranger and visitor services specialist at the Crystal River National Wildlife Refuge Complex, it hosts the “largest aggregation of manatees in a natural ecosystem in the world.”

The creatures, which average ten feet long and weigh between 800 and 1,200 pounds, use the spring-fed waters as a wintertime spa, lounging around until water temperatures in the Gulf warm up enough for them to exit and feed on sea grass and other vegetation while averting hypothermia. Many leave the area in the spring, but some hang out all year round.

The manatees’ presence is a major economic force in the region — between $20 million and $30 million generated per year in Citrus County, according to Vicente. More than 40 manatee tour operators ply Crystal River under permits with the U.S. Fish & Wildlife Service, using dive boats, kayaks and, lately, stand-up paddleboards. Not included in those numbers are local residents who own boats and out-of-towners who rent watercraft.

Vicente and his fellow rangers are kept very busy trying to balance the burgeoning recreational industry with the need to protect an endangered species.

“This is a wintering bedroom for manatees to guarantee they won’t die from hypothermia or cold stress,” he said. “It’s not a theme park, not a petting zoo. Manatees are not here to amuse people. This is a natural place we want to keep wild.”

In 2012, refuge officials implemented what Vicente called “very necessary measures” establishing the King’s Bay Manatee Refuge under USFWS jurisdiction. That means rangers have authority under law to prohibit harassment of the sea cows in the area by imposing fines for offenses like chasing, riding or disturbing a sleeping animal. New speed zones for motorboats also took effect. The designation also allows refuge officials to temporarily close some of the larger springs — such as House Springs, Jurassic, and Three Sisters — for up to two weeks during extended cold spells when manatees are concentrated in high numbers. In the future, the refuge may implement a certification process for the more than 100 boat captains who operate in King’s Bay.

Vicente says rangers have ticketed “dozens” of violators in the past two years, mostly for touching a resting manatee. Fines average a few hundred dollars. But he says tour operators are doing a better job of educating their customers on manatee etiquette than a few years ago.

Indeed, on Biederman’s tour with about a dozen other tourists on a cold January morning, boat captain Greg Harris directed the guests to be quiet and calm and use stealth — “let the manatee dictate our experience,” he said.

“They are going to bump us, pull on your hair. They will grab your arms or legs with their flippers,” Harris said. “These are the guys we can pet. One hand only.”

He got into the water with the snorkelers to ensure everyone was on his or her best behavior. All were able to get up close to several manatees.

“Like 1,000-pound golden retrievers,” Harris remarked later. “I never get tired of playing with manatees.”