After being rescued on a Cape Cod beach in March, a harbor porpoise named Sandy was rehabilitated in Duxbury and released into the Atlantic on Wednesday.

It’s not often you see a State Police cruiser escorting an ambulance to bring someone home.


For Sandy, a year-old harbor porpoise, it was first-class all the way as she was released in the waters off Gloucester on Wednesday night.


Sandy was rescued March 5 by the Cape Cod Stranding Network on a beach in Barnstable.


She was taken to a New England Aquarium facility off the Duxbury coast, and for the past four months she was given around-the-clock care by the aquarium’s team of veterinarians, biologists and volunteers.


Undernourished, ridden with parasites and with a touch of pneumonia, the porpoise was watched by team members at her indoor holding pool 24 hours a day until she began eating on her own.


After Sandy gained nearly 20 pounds and was cleared medically, the aquarium staff set the plans in motion toward her release.


As members of the rehab team began giving her live fish, she became increasingly active.


“She started to swim faster around the pool in the last week, so we thought that was a sign she was ready to be back in the ocean,” said Sheila Sinclaire, a biologist who began working with Sandy in March.


Sandy’s caretakers wanted to make sure release day was as stress-free as possible. Only vital people were allowed near the porpoise, and noise was kept to a minimum.


After being lifted from her pool into a rubber-lined container, she was loaded into an animal ambulance and escorted by a state police trooper from Duxbury to the Harbor Express boat terminal in Quincy.


Water Transportation Alternatives Inc., a company that operates commuter boats between Boston and Quincy, donated the use of Voyager III to bring Sandy back to sea.


Dr. Charles Innis, a veterinarian at the New England Aquarium, said Sandy handled the trip well, despite being unhappy to be out of the water.


“I think it shows how strong she was, that she was up and about and alert, wanting to get out of the crate the whole time,” Innis said.


While traveling on Wednesday, Sandy’s heart and respiratory rates were monitored, and her temperature was kept constant with the use of cold water and ice.


The waters on the South Shore are too warm for a harbor porpoise, so the rescue team traveled toward Jeffrey’s Ledge off Gloucester, where they hoped Sandy’s instincts would take her farther north to Maine or Canadian waters, and to other porpoises.


Near Jeffrey’s Ledge, a special slide was lowered off the side of the boat and slicked down with water before Sandy gently slid off into the waves.


A dive team stood by in case she needed help orienting herself, but she quickly swam away on her own.


“It’s bittersweet – you care for her and make sure she’s healthy. It was time for her to go, but it was also sad to see her go,” Sinclaire said.


The aquarium will still be able to keep track of Sandy. Halfway through the boat ride, an electronic tracking device was attached to the porpoise’s dorsal fin.


In addition to tracking how deep into the water Sandy can dive and how long she can stay under water, the device tells staff at the aquarium where she is.


Just two hours after Sandy’s release, the first data came back from the tag, letting aquarium staff know that she was off the coast of Rockport, Maine, heading north just as they’d hoped.


“The goal is always to bring them back up to proper health so they can be released as soon as possible,” said Belinda Rubinstein, a member of the aquarium’s research department who helped with Sandy’s release.


“It’s a happy day,” she said.


Kristen Walsh of The Patriot Ledger (Quincy, Mass.) may be reached at Kwalsh@ledger.com.