UPDATE: Boston Police identify the body as male.
The Boston Fire Department reports a body was discovered around 9 a.m. where Boylston Street crosses the river. The body was in bad enough shape the gender could not be immediately determined.
On Boston Reddit, ChickenWhiskers describes finding the body:
My girlfriend and I were walking our dog this morning, crossing the Boylston bridge that goes over the river, when I spotted what looked like the top of a man's head bobbing up and down vigorously in the water. ...
On March 20, another body was pulled from the river in about the same place.