The Florida manatees at the Blue Spring State Park manatee refuge in Orange City, Florida, cast a spell over people.

These marine mammals aren't beautiful. They're gray, snout-nosed, and torpedo-shaped with front flippers and a rounded flat tail.

They aren't remarkably large or small. They can grow to 10 feet in length and weigh between 800 and 1200 pounds.

They aren't swift and acrobatic. They glide through the waters slowly. Because they don't maneuver quickly, they are often injured by the propellers of fast-moving boats.

But manatees are downright endearing. Every few minutes they poke their noses above the water to take in a breath of air. And they're sweet toward each other. They swim up alongside each other, resting a friendly flipper on another's back, and glide or rest together. Sometimes they frolic and play silly games, like which one can make the biggest splash with her tail.

As soon as the water temperature in the St. Johns River started getting cold, Florida manatees head to Blue Spring to winter in the constant 72-degree water. The water's clarity and blue-green hue makes it easier for visitors to see manatees here than in St. Johns River and other bodies of water.

Park rangers use watercraft scars on the manatees' bodies to identify them. With three deep gouges on the left side of her tail, Amy is easy to identify. Several young ones always tag alongside her. Like mothers everywhere, she rarely has a moment to herself.

Another manatee, Amber, was easy to spot due to a float attached to her tail. When she was seriously injured by a boat propeller, she was treated and rehabilitated at Marine World, and then released into her natural habitat. A float and satellite tracking belt were fitted around her tail so marine biologists can follow her whereabouts and learn more about manatee behaviors. The exciting news is that Amber is pregnant and if she gives birth while in Blue Spring Run, it will be the first birth there since the 1970s.

To get more informed about manatees, visitors can attend one of Blue Spring State Park's daily manatee programs and learn facts like these:

• Florida manatees, also called West Indian manatees, are marine mammals.
• They can live in fresh, brackish and salt water habits, such as rivers, springs, harbors, bays and inlets.
• Florida's 2009 manatee count was 3,807.
• When Blue Spring State Park began the manatee refuge in 1972, 13 manatees wintered there. The number grew to 301 in 2008.
• Manatees seek refuge in warm waters, such as the 72-degree waters of Blue Spring, because they cannot survive in waters less than 68 degrees.
• They have no natural predators.
• Manatees are endangered due to reduced habitat, manmade barriers to migration to warm waters, watercraft accidents, and more.
• About a third of their deaths result from injuries caused by watercraft.
• Manatees eat the equivalent of 10 to 15 percent of their body weight daily: 100 to 150 pounds of vegetation.
• They come up for air every 3 to 5 minutes.
• When they are sleeping, they can stay under water up to 20 minutes. They come up for air and submerge without waking up.
• Manatees usually give birth before the weather gets cold.
• Milk glands are located under the flipper where it joins the body.
• Babies nurse for 2 months and then begin feeding on vegetation.