Big Shark

The Big Shark was the main antagonist of the 1999 film, Deep Blue Sea.

Biography
This shark and the other two sharks were caught and brought to Aquatica to be used as a test subjects as Aquatica's crew tried to create a cure for Alzheimer's and used sharks for it. They were experimented on and fluids from their brain were harvested to create a cure from them, but their brains were too small to provide enough fluid so Susan and Jim mutated them to increase their brain size.

This had the side effect of them becoming bigger, smarter and more dangerous, developing the ability to swim backwards, although she took it much further than her brethren, and became the largest of them, a monstrous Big Shark and leader of the trio.

She reached roughly 25 feet or 45 feet, while the other two didn't reach even half of her size. Big Shark attacks Jim and bites off his arm, much to the shock of others. Big Shark throws Jim's gurney at the window, breaking it and flooding the lab, killing him in the process. Much later, she jumps out of the pool, grabs a distracted Franklin from behind, drags him into the water and kills him while the remaining small shark swims up to her, rips off his upper body and swims away with it.

The Big One has her next victim was Tom Scoggins, who ended up being devoured while trying to help Carter activate some controls to drain the water from a stairwell leading to the surface. But she’s didn’t want to eat Carter that trying to escape from her and letting him go.

The Big One revealed herself to the last survivors to tries to reach the surface, but she got the fire with vests. As Susan, Carter, and Preacher finally head up to the surface, Preacher ends up being attacked and dragged on the leg by the third and final shark (presumably the big one), but he manages to swim to safety by stabbing the shark's eye with his crucifix, forcing it to let him go.

After tending to Preacher's injured leg, Susan and Carter learn of a horrible realization: the sharks have been herding the team into flooding the facility so that they could escape through the plain steel fences at the surface into the open deep blue sea. Realizing now that the big shark is too dangerous to be set free into the wild, Susan decides that she and Carter would have to kill her.

Carter devised a plan to kill the big shark: he would fire a harpoon filled with dynamite powder at the shark, and that Susan would have to connect the trailing wire to a car battery that will send in an electric current to blow it up. However, the big shark is too far away and too deep for Carter to make a clear shot. In a last-minute effort to get the shark's attention, Susan cuts her hands and dives into the water, causing the big shark to smell her blood. Having attracted the shark's attention, Susan tries to climb out, but the ladder breaks, and despite Carter's attempt to save her, the giant shark devours Susan whole, much to Carter's distress. Despite Susan's death, her effort was enough for Carter to get the shark at firing range, allowing Preacher to fire the harpoon at the shark's dorsal fin, though it pierced Carter's leg in the process. As the giant shark finally attempts to swim out to the open sea, Carter frees himself from the harpoon as Preacher connects the trailing wire to the battery. As a result, the giant shark blows up to pieces, avenging the deaths of the rest of the team, much to both Carter and Preacher's relief.

Personality
The Big One is very extremely scary, mean, cunning, cruel, superhuman intelligent “she’s may be the smartest animal in the world, she’s still animal” by Susan, manipulative, vituperative, savage, dangerous and evil largest shark of the mako sharks.

The largest shark revealed its enhanced awareness by chop off Jim's arm when the latter lowered his guard.

Trivia

 * She is the only shark to kill a human and actually the only thing to do so as she is essentially the only reason of human death in the movie.
 * Her total body count is 9. She directly killed 4 people and indirectly killed 5.
 * Renny Harlin mentioned in the behind the scenes of the movie that she is 25 feet long, and weighs 8,000 pounds. This matches up with the scenes of the actors interacting with the animatronic, but differs drastically from the CGI size of the shark, where her dorsal fin was as large as Carter (who later stated the shark was 45 feet to Preacher at the end).