Parallax Effect Demonstration 2 - Perceived Motion of Stationary Object.
This video demonstrates the perceived motion of a stationary object when viewed from a moving camera focused on a fixed point beyond the moving object.
As the relative position of the camera to the fixed point changes so too does the relative position of any object between the camera and the fixed point. If the camera is zoomed in, thus reducing its field of view, this can give the appearance that the camera is barely moving and the (stationary) object is moving really fast (as it zips "past" the field of view).
This is the so-called Parallax Effect.
This effect can be greatly exaggerated depending upon how fast the camera is moving, how much the camera is zoomed in on the fixed focus point, and how close the object to the camera.
If the object is moving, even slowly, that too can greatly exaggerate the effect.
So, no, that alien video, shot from a fighter jet, that looks like its flying unbelievably fast above the sea is not an alien.