The decision to put a private natatorium in one’s home basement is a judgment that has only a few likely antecedents. One is eithe a lover of swimming or they are up to something fishy. For the family grandmother Áróra (Elin Petersdottir) in Natatorium, the debut film from the Icelandic director Helena Stefánsdóttir Magneudóttir, the latter is undoubtedly the case.

This is a very wet movie. That’s fitting for Áróra, who seems to have something of a non-sexual fetish for water. Her daughter, Lilja, drowned under somewhat murky circumstances and ever since the household pool has been a catalyst of PTSD and a source of danger. Another one of her kids, Kalli, played sickly and almost ghoulish by Jónas Alfreð Birkisson, won’t last much longer under the auspices of his mother, whose medicinal care includes injecting him with fish tank water. His siblings Vala (Stefania Berndsen) and Magnús (Arnar Dan Kristjánsson) seem to avoid the house (and their mother) as much as possible, though she has yet to be completely ostracised. Magneudóttir reveals information about Áróra at an excruciating piecemeal pace and yet the characters always know, even at their most ignorant points, an easy three times, what the audience is privy to.

Magnús’s daughter Lilja (newcomer Ilmur María Arnardóttir), named after his dead sister, runs off to her grandparents’ home in the city to try out for a part in a play — a weird one in which she dons a skin-tight blue bodysuit with colourful facepaint and ornate accessories. Aspects of her costume might hint at the undine tradition, though I’m not sure that makes sense within the story’s overall themes. Her presence generates a domestic panic between the two healthy siblings, who recognise the danger that comes with their mom’s home. Neither of the able-bodied siblings ever makes use of their full willpower to put an end to the situation, yet they both know (and, in their own ways, respond to) the stakes of Lilja’s stay with Áróra. Their non-response, through thematic content and visual presentation, comes across not simply as negligence but also as mythological lite. In myths, characters don’t do things because they make sense but because providence hangs over their destinies. Things happen because they need to. And that’s one way to interpret Magnús and Vala: as role players in a myth that they do not orchestrate.

There is a softness to the creepy images. It’s as if they caress you before incising into more disturbing terrain and carving a place into your memory along the way. Petersdottir deserves much of the credit here for the way her counterfeit niceness overload moves not into passive-aggressive territory but more of the murderous innkeeper tradition. The audience is never given the choice to trust her — her introduction comes by way of fish water injection. Audiences are let in on information to which Lilja and others remains oblivious..

The cinematography from Kerttu Hakkarainen is always on the move. Often the movement is horizontal, almost as if shrinking the space of the house, where almost the entirety of the film takes place. When the camera stops moving, it’s carefully and almost studious — such as in one conversation in the dining room/kitchen between Magnús, his new girlfriend Írena (Kristín Pétursdóttir), and Vala. The two women sit at the table and Magnús, pacing around the room and eager to leave to get back to work but scared to leave his daughter home, has his face obscured by a party streamer (they are there to celebrate Lilja being selected for the play). Vala tells Írena something Magnús never mentioned about their past and the party decoration visually divides the women from Magnús. The unusually still camera from Hakkarainen encourages careful contemplation. It also inadvertently alludes to the male power dynamics at play in the scene, a somewhat singular scene in a film so dominated by women. Even behind the camera, almost 60% of the crew are women.

Caretaking images, including one sudden segment of a catheter being removed from an unconscious Kalli with his penis in a painful medium close-up, interrupt themselves with life-taking images. Most notably, Áróra, perhaps out of grief for her dead daughter but more likely out of a twisted psychopathic bent, abuses near-death and baptismal-like drowning experiences in order to induce mystical experiences in others. At least, that’s what happens to Kali. Lilja, as far as we are aware, shows no sign of any spiritual encounter… and nor does Áróra herself verbalise an interest in any mystical consequence. In fact, she doesn’t talk that much at all.

Natatorium’s best boons are also its banes. The moving camera feels restless by the end of the picture — not necessarily purposefully so, but it’s grating nonetheless. The music from Jacob Groth is well-written and always engaging, though it occasionally arrives to a scene a bit late. The tardiness occasionally makes the film feel cheap, a slander that the actors then pull the film out of. Most crucially, the ambiguity behind Áróra’s poor parental (and murderous) deeds contradictorily holds together one of the film’s main sources of intrigue as well as leaving more to be desired. She is such a blatantly bad person that she begins to stop resembling a mother of any sort; one wonders how much more effective of a character Áróra could have been had her sins risen from a place of motherhood — twisted motherhood but still motherhood — instead from a place of creepy mystery and ultimately blind ​​iniquity. In other words, Áróra doesn’t make sense in its entirety. And that seems to be on purpose. It works to draw the viewer into Petersdottir’s performance but once one gets closer, they may notice the character is ultimately hollow.

Natatorium just premiered at the 53rd International Film Festival Rotterdam.