Other mistake: On the death certificate for Chrissie, the shark's first victim, the date of death is July 1st. But later, on the reward paper posted by the boy's mother, it says that the date of Alex's death was June 29th. Alex died after Chrissie, not before. Also, the form refers to the coroner as the "corner," and Jun 29th 1974 was a Saturday, not Sunday. (00:09:05 - 00:18:10)
Other mistake: In the scene at the dinner table, when Brody's son is copying his movements, after Brody puts down his glass to cross his fingers, you see his son cross them before Brody does. (00:39:20)
Other mistake: The five yellow barrels are not on the Orca when they are getting ready to leave shore. When Quint begins singing, goes and stands at the cabin door, you can see through the front windows that the barrels are not there. With the Orca leaving just moments later, they should have already had the barrels on board. (01:07:30)
Other mistake: When the boy gets attacked on the lilo and everyone is told to get out the water, the group of boys are standing just in front of the pool of blood. The water is too shallow for a shark of that size to swim in without it being seen.
Other mistake: Two errors when Hooper is at the helm...the first is Quint yelling at Hooper "starboard, ain't you watching?"the shark is actually running from the port side of Orca. The second is when Quintbtells Hooper to head SSE...Orca turns to starboard while moving ahead...a SSE course would be a turn to port.
Other mistake: When Cooper is first examining the remains of Chrissy, the medical examiner takes her remains out of a cupboard of sorts, and carries them to a table. He doesn't struggle, and lifts the tray rather easily yet when Hooper is describing the remains of the body, he says "The torso has been severed mid thorax, the right arm has been severed above the elbow, the left arm, head shoulders sternum and portions of the rib cage are intact" The mistake is that Hooper describes way more of the remains than can have fit in the small tray and or be lifted so easily by the medical examiner.
Chosen answer: As mentioned in the movie, the posion was in the needle and the shark's hide was too tough for the needle to penetrate. Hooper had to go in the water so that he could get the needle into the shark's mouth, where the flesh was less tough.
Kevin Howard