The Twilight Zone Season 4 Episode 2

Opening Narration
Narrator: "Incident one hundred miles off the coast of Guadalacanal. Time: the present. The United States naval destroyer on what has been a most uneventful cruise. In a moment, they're going to send a man down thirty fathoms to check on a noise maker--someone or something tapping on metal. You may or may not read the results in a naval report, because Captain Beecham and his crew have just set a course that will lead this ship and everyone on it into the Twilight Zone."