Borrowing heavily from movies like “The Thing” and “Alien,” “Sea Fever” doesn’t have much that’s distinct about it, save for a vivid sense of place. Hardiman (who also wrote the script) imbues her story with strains of Irish folklore and the nitty-gritty of the fishing trade. The saturated visual palette — all greens and browns and neon blues — evokes a hint of fantasy, but the director grounds the movie in a kind of spatial realism, carefully deploying the crust and claustrophobia of the ship to atmospheric effect.

Unfortunately, this rigor doesn’t extend to the plot. In real life, the most fearsome pathogens are those that defy prediction, but contagion movies work best when the threat abides by some consistent rules that can give structure to the stakes. The monster in “Sea Fever” mutates haphazardly to accommodate the story’s dramatic shifts: in one scene, it goes swiftly from predatory leech to a benign wisp, batted away easily by the heroine. The film also seems unsure about its own shape, switching indecisively between creature feature, epidemic thriller and environmental drama without articulating any meaty ideas.

Sea Fever

Not rated. Running time: 1 hour 29 minutes. Rent or buy on Amazon, iTunes, Vudu and other streaming platforms and pay TV operators.