Submarine Seaview Control Room in Opening Scene!
Anyone who's seen "Voyage to the Bottom of the Sea" would realize that the opening scene aboard a non-descript submarine is the control room set of submarine Seaview from the movie and TV series of the same name (also filmed at 20th Century-Fox, incidentaly).
BTW, in another scene from "Flint" Coburn kills one of the baddies by kicking him into a disintegration machine. The machine is a re-dressed prop of the reactor unit from the sub on "Voyage to the Bottom of the Sea".