We sit shivering on our boat, wondering whether we've made a big mistake.
The air temperature is 52 degrees, but the brisk wind makes it feel closer to 42.
Monitor photographer Melanie Stetson Freeman and I have come to the Crystal River on Florida's Gulf Coast with one mission in mind: to swim with endangered Florida manatees.
But now, sitting in the boat with our toes approaching a deep shade of blue, we are beginning to question whether swimming is such a good idea.
Manatee experts say the best time to see significant numbers of manatees is just after the weather has turned really cold. The colder the better, they say.
That's because manatees cannot survive in water much colder than 68 degrees. When the water turns chilly, they tend to congregate in the warm outflow of natural springs like the ones that feed the Crystal River. These natural, clear springs produce water heated to a relatively balmy 72 degrees year-round.
By the latest count, there are roughly 2,400 manatees in Florida. After fighting back from the brink of extinction, the population has remained relatively stable in the 1990s despite efforts to further bolster its numbers.
The manatee has no known natural predators. Its most lethal threats are posed by cold weather, red tide, and humans.
A leading cause of manatee deaths is collisions with motorboats. Nearly every manatee has scars from close encounters with sharp, spinning propellers.
Another major threat to the manatee is Florida's exploding development, particularly the destruction of sheltered, mangrove-fringed coastal regions where manatees feed, rest, and raise their young.
Lure of the gentle giant
In contrast to most of coastal Florida, Crystal River is manatee heaven. For much of the year, a large section of the river is posted with no-wake zones where all motorboats must travel at idle speed, keeping careful watch for the gentle sea cows.
With the growth of so-called eco-tourism, more and more folks are interested in coming to Crystal River to don snorkel equipment and get up close and personal with a manatee.
But the practice is somewhat controversial among manatee experts. Wildlife purists say that such trips should involve looking - but not touching - the manatees. Others say there is little harm in reaching out and gently scratching a friendly manatee that approaches a swimmer.
Strict rules bar swimmers from feeding, chasing, riding, or surrounding a manatee. But the fact is, on busy days at certain Crystal River springs, there are scores of swimmers in and around the manatees and many have no idea about proper manatee etiquette.
To help protect the manatee from harassment, conservationists have roped-off sections of water near springs banned to boats and swimmers.
In theory, this gives the manatees a warm place to sleep close to the spring but away from the outstretched hands of swimmers and the murky water their swim fins produce.
As for our own search for manatees, eventually we overcome our chill-induced reluctance and head across the water in our skiff powered by a sputtering six-horsepower engine.
We cross Mullet Run, pass Buzzard Island and Sleepy Lagoon, then turn east under a small concrete bridge. A half mile up a canal we drop our anchor outside a narrow creek. The shore is lined with palm, oak, and cypress trees draped thick with Spanish moss.
This is the entrance to a line of small springs called The Three Sisters. It is, we've been told, one of the best places anywhere in the world to see wild manatees up close in clear water.
We are not disappointed. At least 25 manatees are lined up like massive submerged logs in the roped off sanctuary just outside the creek. Most are asleep. A few swim in the river nearby. Others are up the narrow creek hovering over the warm springs.
There are mothers with calves swimming at their sides, and underwater we can hear a kind of chirping as they communicate with each other. There are also old males with their backs encrusted in brown algae and youngsters with light gray skin.
Seeing them in the water, it is hard to imagine that these are the ancient relatives of elephants and aardvarks. The average adult manatee is about 10 feet long and weighs 1,200 pounds. They can eat up to 200 pounds of vegetation a day.
The scientific name for the manatee is sirenia, like the irresistible sirens of Greek mythology who tried to coax Odysseus and his crew onto the jagged shoreline with their seductive singing. Are these the mermaids of sailor legend? If so, those men must have been at sea for a long, long time.
Many words come to mind watching these massive marine mammals glide through the water. They are gentle, inquisitive, lumbering, peaceful, perhaps even in their own way, cute. But seductive?
At one point we are among 16 manatees of assorted sizes. The sensation of swimming among them is a combination of amazement and, I admit, a little bit of fear and awe. It is difficult to believe that creatures so large and powerful could also be so gentle and nonaggressive. But they seem to accept our presence.
I like to think that they understand on such a blustery cold day in March that shivering humans in their snorkel gear and insufficient wet suits need to be in the warm spring water just as much as they do.