Continuity mistake: Towards the end of the movie, the Preacher stabs the shark in its left eye with his cross, causing it to bleed. In the later scene, when shark returns to eat Susan, its eye is intact. (01:28:10 - 01:32:45)
Continuity mistake: Near the end when the survivors has reached the surface and LL Cool J gets attacked by a shark. Notice all the blood in the water. Shortly after, when he is pulled up and rescued, you see no blood at all. (01:28:20)
Plot hole: Considering the size and power of the sharks, why didn't the female just jump the fence at the end of the film. It was only 3 or 4 feet above the water at that point. (01:30:10)
Revealing mistake: In the shot when the helicopter is about to crash into the building, take a look at the blade. There is a wire holding the helicopter.
Continuity mistake: The man with the cross has a wound on the left hand side of his head. Later in the movie it has moved down.
Factual error: Despite the massive size of the sharks, there's no way that the waist high water would be completely covering the shark. Right before attacks, no one sees a shark until the dorsal fin comes up out of the water.
Factual error: Late in the film, Susan is wearing rubber aquatic shoes. She goes to her quarters to retrieve the data and decides to electrocute the shark that attacks her. She takes off her rubber wetsuit and stands on it on the metal table to insulate her from the current so she doesn't get electrocuted herself. But, isn't she already insulated by the rubber on the bottom of her shoes? Was this just a reason to get her to take her clothes off?
Factual error: There's no way those dynamite sticks could have produced anything like the humungous explosion at the end of the film. In fact, the most they would have done would have been putting a hole in the shark's skin. (Proven on Mythbusters.)
Continuity mistake: When the shark rises above water with Jan partially in its mouth, its teeth are in about the level of her waist. As Carter grabs onto Jan, it moves its teeth up to the top of her chest. In the wide shot that follows, though, its teeth are back at her waist, then in the last shot of her being pulled underwater, they are up way higher again, at her chest.
Factual error: The explosion at the end of the movie should have killed Carter, he simply couldn't have survived the concussion wave.
Revealing mistake: In the wet lab, just after the helicopter explodes into the tower, pieces of concrete are falling all around Thomas Jane, as he reaches to pull the blonde out of the water. The pieces of 'concrete' bounce all around like the foam pieces they are, not actual concrete.
Factual error: When the rescue helicopter approaches Aquatica, the pilot gives his call sign as "X-ray Alpha two eighteen." Numbers in aviation are read individually, so the pilot should have said "X-ray Alpha two one eight."
Plot hole: Mako sharks have been known to leap out of the water, sometimes into boats. Therefore, it is quite possible, perhaps even more so, for these specialised Makos to jump.
Continuity mistake: At the end, Carter manages to hold onto the perimeter fence, and the shark goes through. The shark then explodes, and Carter is seen being blown off the fence back the way he came, yet when he surfaces, he's now on the other side of the fence.
Continuity mistake: When the shark jumps out of the water and grabs Russell Franklin, it slams him down with his body face-down in its mouth. A few seconds later, in the underwater shot, his body is suddenly face-up in its mouth.
Revealing mistake: Towards the end of the film after Carter is being dragged along by the shark, and shot by the priest, his wound does not bleed at all.
Character mistake: When a helicopter winch operator tries to get the gurney with injured Jim inside the helicopter, he doesn't have any gloves on. No wonder his hand gets injured when the cable breaks loose.
Continuity mistake: In the part where they are climbing up the ladder and there's fire on the roof, just after the shark attack Preacher comes and pulls them up with knotted clothes, then he pulls it in with them through the door. When they go back the knotted clothes are there again.
Continuity mistake: When Samuel L. Jackson is grabbed by the shark (CGI) blood splatters all over the place. In the next shot the place and the water are spotless.
Continuity mistake: Carter puts a bandage on his right arm because of the blood. When he tries to shot the shark the bandage gets larger.
Answer: They viewed her as a villain because it was her research that backfired and caused all of the chaos, even though none of it was intentional and it was a mistake. But audiences can be ruthless and unforgiving at times. However, the ending did feel like a cheap cop-out that created more plot holes. And many do feel she should have survived and completed her character arc. I don't know why they never offered the ending as a bonus feature on the DVD, but fans started a petition on the Change site calling for Warner to release the original ending. Thomas Jane is on board as well, as he's promoting it on his Instagram account. So that's probably the best way to get Warner's attention if you want to see the original ending.