"Blackwater" received acclaim from critics and viewers, with many hailing it as one of the series' best episodes, praising the titular battle and its scale and emotional depth, as well as the acting and visual effects.

Set on edge by his childhood fear of fire and disgusted by Joffrey's cowardice, the Hound deserts his post and renounces his allegiance to the Lannisters.

[4] Showrunners were concerned that adapting the full scale of the battle described in George R. R. Martin's A Clash of Kings would require a larger budget than the $6 million HBO approved for the episode.

[5] As a cheaper alternative, early proposals suggested the battle take place mostly offscreen, with viewers experiencing it through the eyes of Cersei Lannister and Sansa Stark, receiving occasional updates from the battlefield as they sheltered in Maegor's Holdfast.

[6] Benioff and Weiss eventually convinced HBO to approve a $2 million increase in the episode's budget as well as an extra week of filming in order to stage the battle onscreen.

Producers decided to set the battle at night to make it easier to hide any production errors and to save money on special effects.

[5] Benioff and Weiss resisted pressure to stage the battle exclusively on land, which would avoid the difficulties of filming on water, because they considered the naval confrontation to be essential to the season's principal storyline.

[5] Benioff named Saving Private Ryan, Lawrence of Arabia, Spartacus, El Cid, and Zulu as influences on the episode's choreography.

[9] Martin said that Benioff and Weiss gave him "the hardest episode of the season" to write, and that he was forced to weigh budget restrictions against the huge scope of the battle he described in the book.

[8] About a week before filming was set to begin, the episode's planned director had to leave the production because of a personal emergency, and a replacement had to be found quickly.

[11] Benioff and Weiss eventually settled on Marshall because of his work on Centurion and Dog Soldiers, where he created intensive action sequences on a limited budget.

[10] Marshall avoided watching the Battle of Helm's Deep in The Lord of the Rings: The Two Towers because it was, according to him, "an obvious comparison"; instead, he studied films such as The Vikings and Kingdom of Heaven.

[14] Belfast's cold and wet climate was so harsh that weather machines were not needed to simulate the wind and rain, and Benioff insisted that the actors' exhaustion was not faked.

[19] The song also appeared twice in the season two premiere "The North Remembers", in which Tyrion can be heard whistling the melody during a small council meeting, and is later played in the background as Cersei confronts Petyr Baelish.

James Hibberd of Entertainment Weekly attributed this to the premiere's coincidence with Memorial Day weekend, which often reduces television viewership by about 20 percent.

The website's consensus reads: "GoT delivers a thrilling tour de force in 'Blackwater', an epic hour of blockbuster television full of spectacular battle sequences and equally powerful drama.

[29] Alan Sepinwall, who reviewed the episode for HitFix, called it "an epic battle, and an intimate hour" and continued "but what ultimately made Blackwater so impressive wasn't the scope, but the focus".

[33] The episode also received praise for its unsentimental depiction of warfare as a harrowing and costly enterprise, with Emily St. James interpreting it as a critique of "the sorts of political systems that perpetuate it".