"Dark Water" is the eleventh episode of the eighth series of the British science fiction television programme Doctor Who.

The episode was written by showrunner and head writer Steven Moffat and was directed by Rachel Talalay.

It is the first of a two-part story; the concluding episode "Death in Heaven", the finale of the eighth series, aired on 8 November.

In the episode, Danny Pink (Samuel Anderson) is killed, and finds himself in an afterlife called the Nethersphere.

In the episode's climax, Missy reveals her true identity as a female incarnation of the Doctor's arch-enemy The Master, last seen in the 2009–10 serial "The End of Time".

The episode was watched by 7.34 million viewers and received widespread critical acclaim, with the performances of Capaldi, Gomez, Coleman and Anderson being praised.

Scenes of "Dark Water" were removed from the DVD previews sent to reviewers, and a media blackout had been imposed on any plot details that were not released by the BBC.

Michael Hogan of The Daily Telegraph gave it five stars out of five and called it "bone-rattling and suitably spooky fare".

[18] Neela Debnath of The Independent said that the episode was "sad, funny, scary, romantic" and "is everything you could ask for from a Doctor Who finale the day after Halloween.

"[20] Richard Edwards of SFX gave the episode four and a half stars out of five, claiming "...in a series of great Capaldi performances, this is one of the best".

He praised the opening premise and the big reveal at the end and also commented on its allusions to The Tomb of the Cybermen and The Invasion.

[10] Matt Risley of IGN praised the episode for its "tense and traumatic dose of Who", but was critical of the lack of action, which usually went hand-in-hand with the Cybermen.