As the waters cool this time of year, you could hop a plane, fly along the coast toward Florida and watch a natural wonder.

The manatee

Looks like a fat seal with a whiskery puppy dog face.

Grows to more than a half-ton and 14 feet long.

Is among any number of marine, avian and other species migrating this time of year. Wildlife officials urge people to be alert for them, give them room.

Is a federal endangered species — fewer than 5,000 are known to exist; boat strikes are a major threat.

Of the 50 or more sightings made in South Carolina estuaries each year, nearly half are around Charleston.

Sources: U.S. Fish and Wildlife Service, S.C. Department of Natural Resources and Sea to Shore Alliance

“When the first cold fronts move in, it's just like a train of manatees moving south along the beach-fronts,” said James “Buddy” Powell of the Sea to Shore Alliance, a marine ecology advocate that tracks the animals.

Manatees move north from Florida and summer in Lowcountry waters, where there are 50 or more sightings each year. One of the puppy-faced mammals poked its nose from Charleston Harbor for a breath of air last week, wowing staffers at the South Carolina Aquarium.

They don't go back en masse until water temperatures drop to below 70 degrees. With temperatures still largely in the 70s, the animals don't seem to be in a hurry to leave their summer digs.

Manatees are bulbous, seal-like creatures whose lolling, seemingly serene behavior has delighted onlookers for generations. They are said to have inspired the myth of mermaids.

The animals tend to turn up near docks, particularly where a freshwater spigot runs. But they also roam estuaries and tidal rivers as dolphins do, hunting food.

Biologists are now learning something pretty surprising. “As long as the temperatures are warm enough they'll stay,” Powell said, “and they'll stay as long as they can.”

There's even some suspicion that manatees might be gradually relocating. They have been spotted as far north as Massachusetts and now are seen more commonly up and down the East Coast, Powell said.

They might be expanding their range because their population is growing. But it also might be that warmer waters and such threats as boat traffic in water-sport crazy Florida are forcing the animals to move to less-crowded waters and making them more reluctant to return. The “gentle mermaids” tend to poke along, surfacing to breathe, and that makes them vulnerable to hull and propeller strikes.

“As murky as our waters are, they're really hard to distinguish,” said aquarium educator Shelley Dearheart.

So more manatees than we know might summer and loiter around the Lowcountry far into fall.

Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.