It’s admirable — and rare — to see a film as invested in science as “Sea Fever,” even when it’s own science is a little far-fetched. Unlike the many well-decorated experts you usually have floating around monster movies to attempt to bring reason into absurd situations, the heroine of Neasa Hardiman’s oceanic thriller, a budding marine biologist named Siobhan (Hermione Corfield) has theories but not certainty about the parasites that seem to be attacking the crew of the Niamh Cinn Oir, the boat she boards to study patterns of sea creature movement to turn into algorithms that can better chart their trajectories. Even as one by one, the fishermen, who take on Siobhan for some extra income, begins to exhibit unusual symptoms such as irrationality and blood in their eyes, they are more likely to dismiss the maladies as the “sea fever” one gets from having only two hours a sleep a night on the open water, but Siobhan knows better, as does the ship’s engineer Omid (Ardalan Esmaili) and as they work to demystify a situation beyond logic with what knowledge they can be certain of, the film feels refreshingly timely in a time when climate change is denied and vaccines are under attack.

However, “Sea Fever” is first and foremost a good time, assembling a hearty crew for the Niahm Cinn Oir, led by an appropriately salty Freya (Connie Nielsen) and Gerard (Dougray Scott), that under normal circumstances would give Siobahn great bang for her buck with their hard-earned knowledge of the sea. Yet taking a shortcut through the exclusion zone proves perilous when strange creatures, appearing at first to be barnacles, attach themselves to the ship and a blue goo begins to emanate from them, embedding itself into the walls. The ocean that once seemed so vast suddenly feels as if it’s bound to cave in on the ship and Siobhan, realizing the goo may be carrying something sickening into the water supply, sets up a standoff where she can only be seen speculating about the cause while her sea-faring companions feel experienced enough to tough it out.

Hardiman may embrace the tight quarters to create a few claustrophobic scares, but navigates the ship with muscular command with fine work from production designer Ray Ball and cinematographer Ruiari O’Brien to keep “Sea Fever” lively and spry, making the introduction of the parasites with their vivid pastel colors and slick design a strong fit within the world of the film while feeling otherworldly. Also unique is what the film considers heroic, with characters thinking of the greater good in ways you don’t typically see and the strong ensemble of actors allow Hardiman to keep moving at a steady clip when you can often tell where everyone’s coming from with not much more than a look. (Scott and Nielsen make an especially delightful pair with their mutual grit and gravitas.) Ironically, there’s far more to the rest of “Sea Fever” than it appears at first glance and while the water isn’t safe to swim in, the film is well worth taking a dip.

“Sea Fever” will screen at the Toronto Film Festival on September 14th at 7:15 pm at the Scotiabank.