Set in Miami, the series centers on Dexter Morgan, a forensic technician specializing in bloodstain pattern analysis for the fictional Miami Metro Police Department, who leads a secret parallel life as a vigilante serial killer, hunting down murderers who have not been adequately punished by the justice system due to corruption or legal technicalities.
According to Nielsen Media Research, the episode was seen by an estimated 2.28 million household viewers and gained a 1.2 ratings share among adults aged 18–49.
At the station, Debra (Jennifer Carpenter) worried when Masuka (C. S. Lee) reveals that LaGuerta (Lauren Vélez) is running a blood test on Travis Marshall's slide.
Matt Fowler of IGN gave the episode an "amazing" 9 out of 10, and wrote, ""Swim Deep" went off in many different directions at times, but they were always excellent.
Even the deployment of Ghost Harry is merciful in its brevity, and he engaged Dexter in an illuminating conversation about the evolution of his relationship with Deb.
"[5] Kevin Fitzpatrick of ScreenCrush wrote, "While "Swim Deep" certainly takes things in an intriguing direction with both Hannah McKay's story and Isaak's incarceration, we're hoping that the final scene isn't a way of shaking off the big reveal between Dexter and Debra.
We're also not terribly thrilled to see Quinn falling in with yet another bad element, but for now the episode certainly keeps things moving.
All the tension between Dexter and Debra, along with his slow, inevitable march toward finally being exposed as a serial killer, is really paying off.
"[8] Drusilla Moorhouse of Zap2it wrote, "With Isaak, Dex metes out justice that doesn't involve shrink wrap and duct tape.
Instead, he lures the Koshka Brotherhood boss to a Colombian cartel bar, expecting the drug warlords to kill him.
"[10] Billy Grifter of Den of Geek wrote, "It's times like that where Dexter can fall into a habit of messing with the audience because it can, which is a lazy alternative to building a narrative where a surprise is genuine rather than tactically constructed.
The show is managing to juggle a trio of storylines – Deb vs. Dexter, the presence of Hannah, the threat of Isaak – very well, keeping its foot on the suspenseful pedal without even including any major bloodshed.
"[12] Alex Moaba of HuffPost wrote, "So they've reached an uneasy understanding now, and with this relationship seeming more settled - at least for the time being - it will be interesting to see how the show pivots towards its eventual end-game, and if the main conflict will now become Dexter vs. the Ukrainian mob?