Two alien spaceships collide in the depths of space, and a capsule from one vessel crashes into the ocean near the Bermuda Triangle. Five years later, the underwater research facility Oshona uncovers those crystals, and facility manager Mike Olsen [Corin Nemec] retrieves them. As he heads for the mainland, divers Don [Nencho Balabanov] and Jake [Velizar Binev] attempt repairs on the exterior, only to be overwhelmed by a swarm of sharks.
Inside Oshona, Linda Olsen [Vanessa Angel], a scientist and Mike’s wife, joins a tense rescue effort that has deadly consequences. The attack sequence cascades as the sharks threaten Jonas [Jonas Talkington], Vera [Elise Muller], Simona [Simona Williams], Carlo [Atanas Srebrev], and workers Harvey [Binky van Bilderbeek] and Leo [Emil Markov], forcing the facility to lose power and the oxygen supply to drop to dangerous levels. The crew members scramble to survive, while the growing danger outside and the failing life support push everyone to the brink.
Mike boards the submarine USS Roosevelt, commanded by Captain Riley [Corbin Bernsen], and sets course to evacuate the trapped scientists. On the surface, Paradiso Captain [Michael P. Flannigan] sends a diver down to assess the damage, who is swiftly killed by the sharks. A plan to recover the cables unfolds with two men dispatched in a seaplane; disaster strikes when a shark rams the plane, sending one diver overboard to be devoured, while the other struggles to stay afloat.
Back inside Oshona, Jonas realises the crystals are altering the sharks’ behavior by their own presence in the ecosystem. The crystals seem to trigger a psychological effect in the predators, intensifying their aggression. Harvey’s paranoia deepens as fear and confusion spread through the crew, amplifying the sense that something unseen is guiding the catastrophe.
An electrical overload caused by the crystals erupts into a fire in the engine room, stalling the evacuation. With the oxygen dwindling, Mike and Carlo descend in a submersible to restore the facility’s oxygen reserves. They succeed for a moment, but Carlo is killed when the sharks launch another savage strike on the sub. Mike must improvise a hiding place within a crevice and, while there, discovers a second sample of the crystal and manages to bring it back to the Oshona’s control center.
Harvey’s desperation peaks as he attempts to flee in yet another submersible; the sharks ambush this craft, sinking it and triggering an explosion that destroys Harvey. Minutes later, Mike and Linda discover Jonas stabbed to death, and Ben Stiles [Todd Jensen], a Black Ops agent, reveals himself with a purpose to recover the crystals. Stiles shoots Vera, then turns on Leo, who dies trying to create a diversion. He traps Simona in a flooding room, where she drowns.
Stiles pursues Mike and Linda through the flooded corridors, and a brutal fight ends with Stiles subdued—only to be seized by a fatal hunger as a shark swallows him during his bid to escape. In the aftermath, two aliens dive down to retrieve the capsule, and Oshona begins to collapse. Linda nearly drowns, but Mike drags her to safety, and the couple is rescued by Riley in the submarine, with Linda revived. In the quiet that follows, Mike struggles to convince Riley that he truly witnessed an extraterrestrial presence.
