Jupiter, Fla. — As a canoe approached on the sunlit and sinuous river, a woman lifted her paddle from the water and addressed us almost routinely, ''Ten-foot alligator on your right around the next bend.''
We didn't spot the 'gator, nor for that matter did we see any of the resident manatees of the Loxahatchee River, but there were anhingas strutting in the shallows, two watchful buzzards perched atop a dead cypress, hammering woodpeckers, singing wrens, and best of all there was the primordial stillness of this brief and unpublicized waterway. Could we really be, I asked myself more than once that afternoon, only five miles from the coastal resort town of Jupiter and less than an hour's drive from the estates of Palm Beach?
My introduction to the Loxahatchee was arranged by a wily outdoorsman named Bob Bergen, who makes his living showing tourists the unspoiled corners of Florida, a state that is fast losing its innocent ways. Bergen's Tropical Wildlife Tours (4618 Forest Hill Boulevard, Box 060202, West Palm Beach, Fla., 33406; telephone (305) 965-4299) are mostly informative, air-cooled bus trips, but his handful of river runs are the stuff of adventure.
Though the Loxahatchee is just 17 miles long and easily missed by motorists booming down the coastal US 1 toward the Palm Beaches, its anonymity may be short-lived. Or so Mr. Bergen explained to a friend and me as we drove to our launching site in Jonathan Dickinson State Park, a piney tract just north of Jupiter near the Palm Beach and Martin County lines.
''The National Wildlife and Scenic River System has about 200 rivers in it,'' Bergen said, ''and the Loxahatchee is scheduled to be next on the list. It will be the only tropical river in the system, and also the shortest.''
We put in at a widening of the river in the park campgrounds, where one can rent a yellow canoe for $12 to $15 a day. Another way to take on the Loxahatchee , and not an easy way at that, is to rent from Canoe Outfitters of Florida (telephone (305) 746-7053) at the headwaters and paddle for five hours or so to a prescribed point where you're picked up by van and returned to the start.
What you get on a Bob Bergen trip that you can't get on your own is the company and expertise of a self-proclaimed river rat. Even when he has a convoy of six canoes to look after, Bergen provides a colorful running commentary. We were barely on the water when he pulled up to the dense green shoreline. ''If you get hungry you can eat this,'' Bergen said, plucking a handful of leather fern. ''It's so good I eat it with mayonnaise. Try some.''
''Tastes like a weed to me,'' my friend said, and off we glided.
The Loxahatchee is no white-water river. It's not the currents but the denizens that are wild. ''On my last trip we saw a family of three otters, three Muskovy ducks, three raccoons, and Big George, 12 feet long and 300 pounds, the biggest and baddest alligator on the river.''
Under the gaze of two motionless buzzards perched in a dead cypress, we left the main channel and started up Kitching Creek. Now a stillness set in, and as we floated beneath hoods of mangrove, the water took on the sheen of black lacquer. Bergen, lean, a former science teacher who says he is ''at heart an environmental educator,'' identified the occasional sounds that broke the stillness.
''That's a pileated woodpecker talking,'' he said between staccato outbursts. ''In the background you hear a Carolina wren, and that louder sound, that's a guzzling gas hawk, better known as a Cessna 172, probably the most popular plane in the air.''
We had stopped paddling and were drifting on the black surface as the lowering sun sent shimmering reflections from the water onto the enveloping greenery. We slapped at yellow flies and listened to Bergen waxing on his favorite Florida river trips.
''We go to the Peace River, three hours drive from here in central Florida. It's almost a wild river but pastoral in its beauty with perhaps a few summer cottages along the edge. Then there's Fisheating Creek on the west side of Lake Okeechobee, and I also like the Turner River in the Everglades, and the Suwanee. Whatever river I'm on is my favorite.''
He said there is nothing Spartan about his overnight river runs. ''We eat very well. I can get by on vegetables, but our guests expect more, so it's usually steak the first night, then dehydrated foods after that.''
We covered only a short stretch of the Loxahatchee, but a longer run, either escorted or individual, would have turned up some novel sights, Bergen assured us. There are osprey nests, a 450-year-old cypress, a noteworthy strangler fig vine, and the one-time campsite of Trapper Nelson, a hermit who lived in the wilds along the river for decades until his death in 1968. His several cabins remain, and so do the 200 cages in which he harbored animals in a self-styled wilderness zoo.
If canoeing on the Loxahatchee doesn't appeal, one can always see the river from the Loxahatchee Queen, a 28-passenger excursion boat that does three trips a day from the Jonathan Dickinson State Park landing, precisely where the canoes put in. I was surprised to find a craft of that size on such a quiet little river, but then the anhingas, buzzards, and pileated woodpeckers didn't seem to be complaining.