If you were by Falmouth Harbor on Thursday afternoon, it's possible you noticed the tides acting strangely, surging back and forth.
That, said U.S. Geological Survey oceanographer Jeff List, was a tsunami.
According to the Cape Cod Times, the strange activity was "a fairly rare meteotsunami, which originates with changes in atmospheric pressure."
List thought the tsunami probably originated somewhere between New Jersey or New York, and extended from Long Island to Chatham.
The effects of the tsunami were only visible from some parts of Cape Cod, the article reported. Meteotsunamis do have the ability to become dangerous, but no damage was reported on Cape Cod.