On the pier, the girl's father goes from taking a step backward to nearly running backward, and off the pier.
When the sharks near the beach and ocean-goers are retreating, one sees fins and no people, then people and no fins, never both in the same shot.
During the car/truck chase, Marla is in the lab in the back of the truck. The truck evasively swerved left and right, so she is often thrown forward and backward, with the truck's left-right motions. But several time she fells toward the front or back of the truck which wouldn't happen because the truck is not breaking or accelerating hard.
Just as the father climbs back up on the dock after falling into the water, one of the shark fins falls over.