New footage shows authorities removing a decomposed body from a fishing vessel in Boston ... after a group of Massachusetts fishermen caught the body in their net.

TMZ obtained photos and videos showing the body being lifted from the boat and onto a pier in Boston's Seaport District ... with officials from the Medical Examiner loading the corpse onto a gurney and into an SUV.

A heavy police presence was there when the body, wrapped in a tarp, was removed from the boat ... with Massachusetts State Police and Massport cops, in addition to the fire department and EMTs.

As you can see, there was a lot of curiosity ... folks were standing over the edge of the pier looking at the boat deck before the body was hoisted up and taken away for an autopsy.

TMZ broke the story ... the fishermen caught the body in their net on Wednesday, pulling it in about 40 miles off the coast of Massachusetts.

The body was wrapped and is badly decomposed ... and the Suffolk County District Attorney's Office says they can't confirm the name, age or even gender.

Prosecutors say it's unclear if this is a homicide, telling us ... "No conclusions at this point."

Meanwhile, the Coast Guard is also investigating.