Deep Blue Sea (1999) ending / spoiler
The sharks were herding the people through Aquatica to sink it so that they could escape. This is because the top eight feet of the fences are not titanium. Susan, Preach and Carter then attempt to kill the Gen II Mako. It eats Susan and almost escapes, but Preach blows it up just in time. He and Carter are the only survivors.
Submitted by Demonhunter