I am driving south on US41 towards Naples, Florida, in a monsoon downpour and there is not a manatee to be seen. It was the promise of swimming with manatees that brought me to the south-west coast of the "sunshine state" but someone up there forgot to turn off the power shower. It has rained almost non-stop for four days and I'm doubting whether I'll ever glimpse a manatee, let alone swim with one.
Manatees are perhaps one of the most enigmatically engaging marine creatures you're ever likely to get close to in the wild. They belong to the sirenia group of sea cows and they spend their days gently grazing on the beds of sea grass that grow in the shallow, tropical waters off the Floridian coast. From the front they have the hangdog expression of a grumpy old man. From the back they look like a mermaid, complete with horizontal tail flipper.
The tourist brochures promised "swimming with manatees" but that was before the weather got in the way. Everyone says it's unusual because most downpours in summer last only an hour or two in the afternoon before that famous Floridian sunshine breaks through. But I'm beginning to lose all hope. Twice I've attempted to kayak down the Cocohatchee river to its manatee-rich estuary, but on both occasions the rain was too heavy.
Steve in the Cocohatchee Nature Center is optimistic about the outlook. He's checked his "Doppler" and he assures us that the weather front is "moving south". Twenty minutes later we're back in the office wet through. Mark, my guide for the day, mutters something about not "needing no Doppler to tell me when it's raining" and suggests a rescheduling. Two days later, a break in the clouds sees us finally paddling down the Cocohatchee to the sea.
Cocohatchee means "brown water", the colour created by the endless dropping of tannin-rich leaves from the red mangrove lining its banks. Red mangrove is perhaps the most ubiquitous shrub on the coast of south-west Florida. Like other types of mangrove it can live in brackish water, exuding excess salt in the "sacrificial leaves" it constantly sheds. Known as the "walking tree" because of its habit of dropping roots from its overhanging branches, red mangrove can quickly spread out across a body of open water.
Mark tells me that this is the only part of the world where you can kayak with both alligators and crocodiles. Somewhat nervously, I ask whether they are aggressive. "The crocs are the worst," he says. Being just a few inches from water I wonder whether my flimsy kayak would withstand a determined bite. On a lighter note, Mark says that we're more likely to see manatees than crocs – but when?
As we slowly glide down river, Mark points out the rich variety of birds, and how to tell the difference between tricoloured and blue herons. As we get nearer to the sea there is a sudden and remarkable change in the colour of the water, turning from the river's deep, chocolate brown to the milky blue-green of the saline ocean.
I suddenly feel as if I've just crossed one of the thresholds of the vital water cycle supporting the rich Floridian wildlife. The intense tropical heat and humidity cause clouds to form over the sea. These move over the land, unleashing huge volumes of fresh water which slowly percolates through the channels of the swampy Everglades and down rivers such as the Cocohatchee, where it meets the salt-water source where the cycle begins.
On one of those rainy days I took off to do a boardwalk in a little bit of the Everglades. Corkscrew swamp, named after a meandering river, is an eerily beautiful place. Apart from the heat and humidity (and mosquitoes), the first thing that hits you is the noise. Not so much a noise as a cacophony of sound. Strange metallic songs, which must have come from frogs, periodically rise to a hysterical crescendo. The buzz of crickets act as relentless background percussion to deep bass vocalists – half grunting, half barking. These could only have been the calls of male 'gators lurking beneath the bald cypresses.
No trip to south-west Florida should be complete without a mini excursion into its swampy interior. This is the dark heart of the Sunshine State, untamed and untamable. Here, the struggle of life is writ large. The roots of huge strangler figs embrace their host trees in a deadly game of who can climb highest, and stay in the sunshine for longest. Endangered ghost orchids, with six-inch, nectar-filled tubes extending from their white flowers, cling to the sides of trees waiting to be pollinated by the equally long tongue of the giant sphinx moth. The roots of ghost orchids blend in with the bark of the trunks on which they hang, making it seem like their flowers are floating phantom-like in the twilight. I was lucky to see one in flower from a telescope arranged on the boardwalk.
Other "air plants" and lichens of every hue cling to the trees. The greatest tree of all is the bald cypress, some of which are 600 years old and 130ft high. The bald cypress is unusual in that it has no tap roots for anchorage. Instead, it grows "knees" that sprout vertically from its roots, acting like buttresses to protect the tree from tropical storms. These strange structures interlock between the trunks, acting as a dense mat of shallow roots that reinforce each other.
But there are no manatees in Corkscrew, so I'm heading north on US41 to the barrier islands of Sanibel, Captiva and Pine Island, so called because they act as buffers against the storms and hurricanes that come in off the Gulf of Mexico. There is no shortage of good hotels along the US41, ranging from the comfortable and affordable Double Tree to the extravagant and spectacular Hyatt at Coconut Point. The latter is an architectural pleasure dome of palm trees, marble and night-time swimming – think late Roman Empire. In contrast, a simple yet exquisite place to eat turned out to be Randy's Fish Market and Restaurant on the way to Naples. No frills, just good, fresh fish dishes and a particularly delicate battered shrimp.
The weather is now back to normal – intense sunshine that breaks each afternoon to form a few heavy clouds and a quick downpour before clearing up once more for a spectacular Floridian sunset. From Sanibel it is possible to take a boat cruise out to the beach of Cayo Costa Island, a protected state park. This is one of the most exposed beaches in south-west Florida, with nothing in between it and the vast, hot expanse of the open Gulf. Shell collectors come here in the hope of finding the best specimens the sea throws out.
The significance of shellfish to the area goes back centuries, being an important source of protein for the local natives since they first arrived here more than 6,000 years ago. The Calusa Indians even used waste shells of whelk, oyster and conch to raise the foundations of their homes as protection against flooding. Today, these ancient middens have turned into verdant hillocks on which the rich have built magnificent mansions.
On the final leg of my journey I stay in Tarpon Lodge on the northern end of Pine Island. Rob Wells, the owner, tells me that the lodge was originally built in the 1920s and has been used for many decades by boaters fishing the shallow, but rich fishing grounds of Pine Island Sound. He takes me out on his boat to show me the sights. We see the old fish houses built on stilts, where catches were landed and sold nearly a century ago. On our way, a couple of dolphins come to play in our wake. "It's a lazy way of spending an afternoon," says Rob.
We have lunch in the Dollar Bar of Cabbage Key, a small island in the sound, then take off around Useppa Island to view more mansions-on-middens. Later on we visit a small, uninhabited island which has, rather inexplicably, become home to a thriving colony of birds of all descriptions. South-west Florida is famous for its birds – I even managed to spot the rare and threatened roseate spoonbill on the Cocohatchee.
The local beaches are made of white sand composed of crushed and eroded seashells. While swimming on one of these beaches, pelicans dived within feet of me to catch fish. On another occasion, I witnessed an osprey patrolling the water before it, too, dived just feet away from where I swam.
But the most memorable moment came almost on the last day of the trip. This was the same beach where I had seen ospreys and pelicans and now, suddenly, I could see five or six dark underwater shadows coming in my direction. Suddenly, a huge flipper was thrown into the air and flopped down with a gentle splash. A pod of manatees swam into my space, emerging now and again to breathe through their whiskered snouts, spraying water as they snorted. Their dark shadows came closer and closer and at one point they seemed to snuffle in the sand around my feet, like the snouts of friendly but slightly scary hounds. The little ones seemed to be well guarded by the larger adults. But although their presence seemed like an eternity, no sooner had they come on the scene than they had gone. They continued along the beach until they were lost from sight
My ambition was fulfilled. I had swum with manatees, and when I least expected it. True to type, they were as gentle as their reputation. They came quietly and had left in silence.
How to get there
BA Holidays (0844 493 0758; ba.com) offers a seven-night fly-drive to Miami from £432 per person, based on two sharing, for departures during December 2008, including return BA flights from Heathrow, all-inclusive car hire and UK taxes. Book by 11 November, subject to availability. DoubleTree Guest Suites, Naples (001 239 593 8733; doubletree.com ), offers rooms from $89 per night. Hyatt Regency Coconut Point Resort & Spa, Bonita Springs (001 239 444 1234; coconut point.hyatt.com ) offers rooms from $115 (£72) per night, and Tarpon Lodge and Restaurant, Pine Island (001 239 283 3999; tarponlodge. com) has rooms from $189 per night.
Naples, Marco Island, Everglades CVB (001 239 225 1013; paradise coast.com ), Fort Myers & Sanibel (01444 461642; fortmyerssanibel .co.uk ), Visit Florida (0870 770 1177; visitflorida.com/uk ).