On this crisp winter morning, I am stranded on the back of a frisky -- and thankfully vegetarian -- 455-kilogram giant. I feel the warmth of its massive body as it pushes me slightly above the water's surface.
Snorkelling with manatees in Florida's Crystal River, 120 kilometres north of Tampa, is like taking a bath with elephants, the closest land relative to these aquatic giants. Here, snorkelling visitors have a once-in-a-lifetime chance to touch an endangered 45-million-year-old oddity.
Manatees look like giant grey balloons that have been tied off at each end. Their wrinkly heads and paddle-shaped tails are much smaller than the middle section of their plump bodies. These gentle mammals spend the North American winter months in Florida's temperate, 21-degree freshwater rivers, where they graze on greens, including the algae on the bottom of our pontoon boat, and receive belly scratches from snorkelling humans.
While reclining on this aquatic couch and pondering an escape, I suddenly feel something bumping into my legs. I turn my head and spot three more manatees, eager to join the action. As the gentle bully holding me hostage finally lowers me back into the water, the others begin to nuzzle me, inspecting my long hair, which they seem to confuse with seaweed.
I can't see anything but whiskers and wrinkly snouts. They remind me of walruses without tusks.
Manatees are a protected species -- there are about 3,000 left in Florida, according to a 2006 aerial survey by the state's Fish and Wildlife Conservation Commission -- and the rules are strict when dealing with them. They basically sum up to: Let them come to you. If you pursue a manatee that has decided to leave, it's considered harassment.
I begin to massage the tough grey skin of one of the beady-eyed monsters, then quickly switch among the four of them as they roll around to expose their giant underbellies. Impatient with my efforts, one sinks down and grabs my right leg with its front flippers. They are equipped with nails like those on an elephant's foot. I quickly provide my scratching services to appease this demanding client. If these giants weren't so puppy-like, this could start to be stressful.
Our seven-member group, led by a guide from a nearby dive shop, has been on the river since sunrise, when manatees are most active. (Local hotels also rent boats for private excursions.) Pelicans and cormorants bob on the water, which steams in the chilly, four-degree air.
Manatees need warm water and cannot survive long in colder environments. If water temperatures drop below 15 degrees, the animals become sluggish and stop eating. In this fertile river, they consume the equivalent of 10 per cent of their body weight daily. In spring, they migrate back into the open sea.
The creatures' most dangerous enemies today are the boats that occasionally collide with them. The streaks and cuts we see on many manatees' backs and tails are proof of this fact. A loss of habitat also threatens the ancient species.
After an hour of playing with about a dozen of the mammals, it's nap time. The manatees slowly sink to the river bed three metres below, burying their snouts in the silt while their tails stay slightly afloat. Normally they come up for air about every five minutes, though they can stay submerged for as long as 20.
When it's time to take a breath, their snouts gradually rise to the surface like a buoy. A long, slow inhale is all we can hear before the animals sink back to the bottom.
For more information, visit http://www.swimwithmanatees.com and http://www.visitflorida.com.