When I did a research, most of the sources say that orca is one of the fastest. But I could not find a source that says it is actually the fastest.
Some sources say that Dall's porpoises rival orcas in speed. And there are other kinds of porpoises and dolphins that comes into question.
Is there any scientific research with measurements? Or does anyone have any detailed knowledge about this topic?
(Also it would be nice to know top 10 fastest marine mammals, so the question becomes: what are the fastest marine mammals?)
Note: This scientific research might be difficult to conduct also so you can explain the situation as well.