The surface shots of the 'killer whale' are indeed of Orcas; but the underwater shots are of pilot whales (as nearly harmless to humans as are Orcas).
Mr. Nelson states incorrectly that killer whales (Orcas) can not see very well underwater, being able to sense movement more easily.
The entire plot of this particular episode is invalid; Orcas, also known as 'killer whales', have seldom been known to attack humans despite being voracious predators of many forms of seafaring life.