As other reviewers have remarked, 'Submerged' is pretty good initially at building tension as the heroine (Roberts) begins to experience shocking supernatural encounters with apparently drowned schoolgirls (are they figments of her imagination or victims of some sinister crime), but the story soon drifts off course becoming a surrealist experiment that lacks coherency. The climax - whilst still reasonably violent - opts to forego a conventional crowd-pleasing ending for something more cerebral which might not satisfy all tastes.
Semi professional acting and cinematography although some of the location work was effective, albeit the topography didn't always match e.g. In one scene there's mangroves and then a suburban-looking creek, although it was sometimes difficult to distinguish what was being imagined vs what was reality (which I also experienced during the gaol scenes near the end when McCallum is being released).
Sometimes eerie, the film creates tension but fails to deliver tangible shocks, preferring abstract visuals to on-screen violence with a couple of minor exceptions when Roberts is being pursued at the film's climax. I wasn't always certain if what I was seeing was deliberately illogical, or just the consequence of a nano-budget and under-developed plot; there was certainly some atmosphere at times, and the main character's apparent ESP abilities was an interesting premise, but overall it had the look and feel of a student film, lacking plot detail and technical polish.