Revealing mistake: There's one bit where we see the shark slamming into a boat and gliding along the side with its mouth open. Not only does the shark's latex mouth bend beneath the snout, narrowing from pressure, but within the mouth you can clearly see yellow hydraulic tanks to open the mouth. (01:22:05)
Visible crew/equipment: When Brody drives across the deck and then onto the ferry, as he does you can see the large shadow of crewmembers and a camera set up, standing on a high ledge above, cast on Brody's Amity Police van. (00:03:20)
Answer: For what it's worth, in the novelization the shark is a female and pregnant with the offspring of the first movie's shark, but that's not brought up in the film at all.