Crystal River, Florida  - Boo is convinced that manatees prefer chubby companions. The heavyweight aquatic mammals, sometimes known as sea cows, have no time for slender snorkellers "but they swam right up to me," enthuses the ample lady from Texas.

Perhaps a pot-belly encased in a matt black wetsuit presents the well-fed creatures with a mirror image of their bulky selves. In any case, this is the third time this week that Boo, a 50-something with a shock of red hair, has squeezed herself into a close-fitting, neoprene outfit for the pontoon boat trip across Crystal River, a warm water site off the Florida's Gulf Coast north of Tampa.

This is a grey and rather dull morning which makes it ideal for sea cow-spotting, says captain Greg Harris. During the cooler months of the year, the plant-eating mammals love to hang out around the warm springs along Florida's western coast. To ensure his passengers stay warm in the chilly air, the skipper is handing out beakers of steaming hot chocolate.

The holidaymakers on board are happy to forget any ideas about staying slim. After all, there's no beach around to lounge on and if the main attractions hereabouts are happy to weigh in at an average of 1,500 kilos why should the onlookers worry about counting calories?

Crystal River is effectively the only place in North America where tourists can experience Florida's endangered manatees at such close quarters. As a result, most people who want to swim with the loveable, brown beasts end up in the small town of the same name.

Only around 3,500 people live in Crystal River, which makes it the second-largest community in Florida's Citrus County. The town is some 90 minutes by car from the tourist bustle in Orlando and makes much of its status as being the "gem" of Florida's Nature Coast".

Mice and other creatures around these parts are plentiful too and unlike the animated versions at Disney World in Orlando they are very much alive. A total of 19 endangered or threatened species, including birds, crabs and rare flowers, are native to the nature coast, which stretches in the north-west from Clearwater to Ochlockonee Bay. Among them is the West Indian manatee, the largest of three sea cow species.

An estimated 2,500 manatees are to be found around the world and their numbers have been growing after centuries of being hunted for their meat by indigenous Caribbean peoples. Polluted waters are the main threat to their well-being these days, but the slow-moving mammals are also vulnerable to being struck or slashed by the propellers of boats.

SeaWorld Orlando has its own manatee rescue and rehabilitation centre with a team of rapid response experts on call 24 hours a day. One of the highlights of the "Save the Species Tour" takes visitors behind the scene at the theme park's facilities for nurturing wounded or orphaned manatees back to health. Baby manatees often need to be bottle-fed every few hours and in one case, experts developed a cast made of wetsuit material for a wounded sea cow. Around 300 animals are returned to the wild every year.

Manatee rehabilitation is an important aspect of the work carried out at the Homosassa Springs Wildlife State Park where the creatures get a daily feed of plants and enjoy warden protection. The animals can be spotted from the Fish Bowl, a floating underwater observatory. Other park inhabitants include cougars, bears and alligators who occupy their own habitats in a complex which reminds more of a zoo than a wildlife reserve.

The nearby Crystal River National Wildlife Refuge is the most important sanctuary for manatees. According to skipper Greg, some 350 of them spend the winter at the calm and spacious Kings Bay on the upper stretch of the river. Fed by a network of warm springs, the temperature of the water here hovers at around 22 degrees centigrade. Kings Spring is the largest source of spring water usually the first port of call for snorkellers.

The water here is murky, but Boo and the other visitors can see the shadows of the leviathans through their goggles. It is hard to see though how America's discoverer, Christopher Columbus, could have mistaken them for mermaids, said Marilyn Margold, director of the Parker Manatee Aquarium in Bradenton.

Margold's aquarium, two hours by car to the south of Crystal River, is home to the oldest living manatee in captivity - Snooty is the official mascot of the facility and arguably one the most famous residents in the county. Interestingly enough, the West Indian manatee belongs to the scientific order Sirenia which might explain how it came to be associated with mermaids, the mythical half human, half-fish creatures of mythology.

A stream of bubbles eventually betrays the presence of Snooty's relatives in Crystal River. Captain Greg has taken his visitors to Three Sisters spa where the water is sparklingly clear. It is possible to make out the shadows of five creatures in the protected zone which is cordoned off with ropes and buoys. The sea cows are slumbering, but when the visitors mingle and dozens of snorkels start poking out of the water the gentle giants awaken.

One of the sea cows wobbles from left to right and seems to be gazing at the flipper-less interlopers. It's the signal for the snorkellers to hold their breath and puff up their breasts and stomachs in a bid to look as rotund as possible. The ploy works and the manatee seems to wink at them with its big round eyes while at the same time allowing visitors to stroke its folded, wrinkly skin.

Internet: www. visitflorida. com, www. visitcitrus. com (dpa)