|Date:||July 24, 2019|
In an underwater facility, a team of scientists is doing research on mako sharks to help in the re-activation of dormant human brain cells like those found in Alzheimer’s disease patients. After one of the sharks escapes the facility and attempts to attack a boat full of young adults, financial backers send corporate executive Russell Franklin to investigate the facility. In the laboratory, doctors Susan McAlester and Jim Whitlock prove their research is working by testing a certain protein complex that was removed from the brain tissue of their largest shark. However, the shark awakens, and severs Jim’s right arm. Brenda Kerns, the tower’s operator, calls a helicopter to evacuate Jim, but as he is being lifted, the stormy weather causes Jim to fall into the shark pen. The largest shark grabs Jim’s stretcher, and pulls the helicopter into the tower, killing Brenda and the pilots, as well as causing violent explosions that severely damage the facility.
In the laboratory, Susan, Russell, wrangler Carter Blake, marine biologist Janice Higgins, and engineer Tom Scoggins witness the shark smash Jim’s stretcher against the laboratory’s main window, drowning him, and flooding the facility. The group goes to the facility’s wet entry, where they plan to take a submersible to escape. Upon being confronted, Susan confesses to the others that she and Jim genetically engineered the sharks to increase their brain size, as they were not large enough to harvest sufficient amounts of the protein complex; this has the side effect of making them smarter but more deadly. When the group reaches the wet entry, they discover that the submersible has been damaged. While delivering a monologue emphasizing the need for group unity, Russell is dragged into the submersible pool by one of the sharks and devoured.
The remaining crew opts to climb up the elevator shaft at the risk of destabilizing the pool. In the process, Janice loses her grip and falls into the shark-infested water. Despite Carter’s attempt to save her, one of the two remaining sharks drags Janice down under, killing her. In the facility’s kitchen, which has been partially flooded, cook Sherman “Preacher” Dudley, whose parrot is devoured in the process, manages to kill the first shark with an explosion. He then makes his way to the elevator shaft, where he encounters Carter, Tom, and Susan. Carter and Tom go to the flooded laboratory to activate a control panel that drains a stairway to the surface, while Susan heads to her room to collect her research material. Carter and Tom reach the control panel, but the largest shark storms in, ripping Tom apart and sabotaging the controls. In her room, Susan encounters another shark, and manages to kill it with a power cable, destroying her research in the process.
After regrouping, Carter, Susan, and Preacher go to a decompression chamber, and swim to the surface. Carter realizes that the sharks made them flood the facility, so they could escape through the weaker mesh fences at the surface. In an effort to distract the last shark from escaping to the open sea, Susan cuts herself and dives into the water. Although she manages to distract the shark, she is unable to get out of the water. Carter dives in, but is too late to save her from being devoured. While Carter is grabbing hold of the shark’s dorsal fin, Preacher shoots the shark with a harpoon, but also pierces Carter’s thigh. As the shark breaks through the fence, Carter orders Preacher to connect the trailing wire to a battery, sending an electric current through the wire and to an explosive charge in the harpoon, killing the shark. In the end, Carter managed to free himself in time, and joins Preacher to see a workers’ boat en route on the horizon.