On Sunday, a Chambers County sheriff’s deputy spotted an unusual creature swimming up a channel near Baytown. It turned out to be a manatee, a sea mammal authorities believe came west for the summer from Florida and didn’t make it back before last week’s cold snap, which cooled the waters of Trinity Bay below the temperature that manatees can tolerate.

Now, 19 years after the Houston area’s last manatee drama, authorities are preparing to try to rescue the latest arrival before it perishes in the chilly bay waters.

“The cold water makes them stressed, it makes them really tired, just like if you or I were out in a snowstorm,” Chambers County Sheriff Brian Hawthorne said.

The animal might be brought to San Antonio.

The male manatee, part of an endangered species, is isolated in a somewhat sunny spot next to a warm water outlet from the NRG plant in Baytown. Barriers were in place Monday to stop the manatee from swimming off, and boat access was restricted so he is not disturbed by the public.

“He’s already showing some signs of cold stress, so that is a concern,” said Heidi Whitehead, operations coordinator at the Texas Marine Mammal Stranding Network. “Once the water temperature drops below 68 degrees it’s too cold for them to survive. It is necessary for us to relocate it.”

Teams from the stranding network, the U.S. Fish and Wildlife Service and SeaWorld San Antonio are working out a plan to get the so-called “sea cow” out of the water and onto a transporter. It’s likely crews will have to resort to carrying the 700-pound animal by hand from the bay to a waiting vehicle because access to the water’s edge is limited.

Relocation was to start early Tuesday, according to NRG spokesperson David Knox. If all goes as planned, the manatee will be brought out of the water and loaded onto a truck to be taken either to either Galveston or to SeaWorld, depending on its condition.

If the manatee is judged to be well enough, SeaWorld San Antonio, with a higher level of veterinary care, would be the first choice for rehabilitation. If its condition is more precarious, crews will take it to the closer Marine Mammal facility in Galveston.

“We will decide how critical he is once we get him out,” Whitehead said.

In the rescue operation, divers will attempt to place a net around the manatee and tow him to the water’s edge. Then it will be all hands on deck to carry the animal to the waiting truck. Crews will work to warm him up and keep him wet while a decision on where to take him is made.

helen.alexander@chron.com