Neither Mr. Wizard, Beakman, nor Bill Nye the Science Guy (not even Dr. Science--he's not a real doctor!) could beat Dr. Earl S. Herald talking to Fleet Admiral Chester Nimitz about submarines, to Dr. John Lawrence about high-altitude medicine, or to an FBI agent about forensic science (with a demonstration of how fast he could draw and fire his revolver). And then there was always the "animal of the week"!
Some of the old programs are supposed to be available at the Internet Archive, which gives access to the Prelinger Archives. There are also some clips here.
Dr. Herald was superintendent of the Steinhart Acquarium at the California Academy of Sciences, an expert on fish.
Centropyge heraldi, type specimen collected at Bikini Atoll, where Dr. Herald did marine surveys after the atomic bomb tests there. (Picture from FishBase.)