Boston’s beleaguered commuters have probably heard it all before when it comes to reasons for delays, but ferry riders this week encountered an unusual one: A whale has taken up residence in the harbor.

“Ferry service may experience minor delays,” the Massachusetts Bay Transportation Authority warned on Wednesday, “due to the presence of a juvenile humpback whale in Boston Harbor.”

The young whale is believed to be the same one that has been hanging around since late July in the harbor, where they are commonly seen but rarely take up residence.

On Tuesday evening, the whale was seen near the Lynn Ferry, prompting the M.B.T.A. to take caution with its ferries (which carry only a tiny fraction of Boston transit commuters).

As of Thursday afternoon, the whale’s presence has resulted in only one ferry delay (by less than five minutes), and at least one very interesting fishing trip.

Andrew Mahr, a retail real estate consultant and developer, was out fishing early Wednesday morning with his friend, Jake Gatof, who was captaining their boat, when they recorded a video of the whale breaching and then landing in the water with a magnificent splash.