The Underwater Menace is the half-missing fifth serial of the fourth season in the British science fiction television series Doctor Who, which was first broadcast in four weekly parts from 14 January to 4 February 1967. Only two of the four episodes are held in the BBC archives; two remain missing. Episode 2 is the earliest surviving episode to feature Troughton starring as the Second Doctor (he previously appeared uncredited in The Tenth Planet) and the earliest surviving episode to feature Hines as Jamie.