The series is set in the fictional Irish village of Redwater, where the residents are hiding a dark secret, and features an ensemble cast.

[3] Redwater is described as a "very little romantic seaside town",[4] and "a tiny, picturesque Irish harbour village, a quiet rural idyll by the sea where the Kelly and Dolan families have lived for generations.

Treadwell-Collins confirmed that "the discovery that Kat has a secret son will [...] ultimately lead to the Moons realising that the answers to so many questions lie across the sea in Ireland.

"[7] Director Jesper W. Nielsen said the series is "About how one woman's search for a lost child opens Pandora's box; revealing the terrible lies and secrets in the little village of Redwater" and "about how the strong bonds of love in a family can hold everything together, and yet at the same time—destroy everything.

[11] Fionnula Flanagan, who plays Agnes Byrne in the series, confirmed that it is about "the suppressed whisperings and shoulder nudges that were for decades a feature of Irish rural life".

[19] Episode 1 writer Matthew Graham said the series is family-based and character-based, "emotionally real and raw" with "a heightened realism at times".

Treadwell-Collins came up with the idea of setting the series in Ireland when he was on holiday in New Orleans on St Patrick's Day, and he saw people having fun but also claiming to be Irish.

[24] Treadwell-Collins called it the "perfect time" for the characters to be taken "out of their comfort zone" and added that his team were "creating a whole new drama that stands apart from EastEnders while taking our style of storytelling to a place of stories, myth, secrets and immeasurable beauty.

[17] Speaking in reference to the show, Wallace commented, "I have always loved working on EastEnders so when I heard of this new drama to take Kat and Alfie outside of Walford, I couldn't believe our luck.

[30][31][32] Treadwell-Collins said that he would not be working on a second series as he had left the BBC but had spoken to producer Victoria Wharton about it and had "[started] putting plans in place about what would happen next.

However, the series was delayed for unspecified reasons[37] and on 17 October 2015, it was announced that the pair would return to EastEnders, appearing over the Christmas period to set up the storyline that sees Kat discover she has a son and Alfie reveal his tumour.

[7] Richie and Wallace first saw the scripts for Redwater on 13 January 2016,[38] and it was confirmed that filming would start after they finished touring with the stage show The Perfect Murder,[38] which was scheduled to run from 2 February until 2 April 2016.

[33] It was announced on 30 April 2017 that EastEnders would make a "subtle reference" to Redwater in May, "in a bid to keep the two shows in the same universe", revealing that Kat and Alfie have arrived in Ireland.

[61] The reference was made in the episode shown on 16 May 2017, two days before Redwater's UK premiere, in which Kat's relative, Stacey Fowler (Lacey Turner), receives a postcard from the pair.

[64] The music for Redwater was scored by Natalie Holt for synthesizers, guitar and a 12-piece string section, and was performed by the London Metropolitan Orchestra, led by Thomas Gould and conducted by Andy Brown.

[66] Music from Irish bands, including Pursued by Dogs, Little Green Cars, Kíla and Ham Sandwich, also features in the series.

[60] Fionnula Flanagan was confirmed to be having a main role in the series on 11 April 2016, when she said her character, named Agnes Byrne,[69] was "full of secrets, deceit and manipulation.

[70] Ryan Burke, Anton Giltrap and Eoin Daly appear in the series as young Andrew, Kieran and Dermott respectively, and Orla Hannon plays Iris Dolan.

Dermott learns that Bernie is looking into something about Lance on Adeen's phone, so he makes a hoax call to get her on her own and blags his way into the garda station, where she goes into labour.

Kieran tells Bernie that he remembers Dermott letting Iris die on the boat and suspects he was involved in the Cois Dara fire.

Padraig finds Adeen crying by the side of the road, and later takes her to get an emergency contraceptive pill because she had sex with her friend Jimmy (Mark McKenna).

Roisín and Padraig argue about him not making sure there is money in their bank account for the morning, and when he asks why she did not leave him years ago, she says she did.

"[88] Tom Eames from Digital Spy called the series a "bold move from the BBC" that "looks like a show that is a must-watch whether you're an EastEnders fan or not.

"[91] Sean O'Grady from The Independent said, "it's an un-soapy, unclaustrophobic sort of production, and a storyline about a long-lost son adds the necessary emotional stress.

He opined that Dermott was "the show's most unlikely character", calling him "a 33-year-old bearded hipster priest [...] who accessorises his collar with a hoodie and a donkey jacket [and] flies into a rage at the sight of orange juice".

[94] Harry Guerin, writing for RTÉ.ie, said, "the first episode suggested that the clichés won't pile up" and "when Redwater focused on being a thriller (both whoisit and whodunit) there was much to savour—excellent performances, a swirling mist of grief and guilt, an eerily relevant story about forced adoptions, and the growing sense that the just-arrived wideboy and girl from Walford are waaay out of their depth."

He said, "While Kat shines in Redwater, it's fair to say that Alfie seems a little bit lost and directionless in the first episode, with even scenes of him experiencing weird visions and nearly dying (twice!)

[98] Following episode 6, which ended on multiple cliffhangers, Sophie Dainty from Digital Spy said that it was "undoubtedly everything the show had originally promised it would be—dark, gripping, enchanting and excellently written" but it "offered very few answers for the fans who had committed six hours of their lives to this".

[99][100] In the United Kingdom, the second episode was scheduled against ITV's Emmerdale for 30 minutes, and was watched during its BBC One broadcast on the night by 2.7 million viewers.

Aoife Kelly of the Irish Independent noted that the return of The Sunday Game on RTÉ2, airing in the same slot as Redwater, may have impacted its ratings.