A harpoon hits the baby shark near the dorsal fin, but the shark never gets a wound.
When Mike and Sean are having breakfast after Kathryn leaves, Mike brings over a pot of coffee which barely has enough for a cup in it. In the next shot, the pot is is 3/4 full.
When the water is safe to enter for repair, Mike is lowered into the lagoon attached to a rope and umbilicals (oxygen hoses). In the next shot, he is only wearing an oxygen tank. When the mother shark appears and Calvin gives the order to "get 'em up," the rope and umbilicals reappear, then disappear when returning to Mike. It is standard commercial underwater arc welding practice to always be attached to a rope and umbilical for safety reasons. Mike was lowered by a winch, which could have been used to alert him and bring him to the surface. The helmet (also standard) would have had a communications device in it to keep in contact with the surface.
Before the eight girls water skiing fall over, after being scared by the shark, a shot below the water shows ten skis above. There are only eight skiing, and all are using just one ski.
In the scene where Mike and Kay are being chased by the baby shark near the surface they are riding on the back of the dolphins. When they breach the surface and are pulled through the water you can clearly see a crowd in the background stage. There should not have been a crowd there since the park was not open at the time.
When the shark in the public observation pool gets sick, Kathryn jumps in and starts stroking the shark's skin back and forth. That should've hurt her hand; shark skin is smooth from nose to tail, but rough from tail to nose. Carpenters once used shark skin as an abrasive.
The shark snarls and growls. Sharks have no vocal cords.
Sharks can't swim backwards. It's physically impossible. Their fins are not flexible like other fish. They can go backwards by stopping and falling backwards. However, the shark in this movie backs out of a filtration pipe, and it is implied that it used the pipe as a hiding spot. There's no way it could get out of the pipe once it got in.
When they are looking for the shark, Kathryn Morgan's attacked by the baby shark, who tries to bite into her oxygen tank and doesn't let go. However, in reality sharks hate the taste of metal and he would've let go instantly. Shark bites are also usually caused by the shark trying to determine if the creature it encounters is food. Upon biting into the tank, he would've concluded that the creature (Kathryn) isn't food and let her go. Furthermore, the pressure of the baby shark biting into the tank, would've caused it to break.
Philip refers to the shark as him when it has already been called a female. Right after this slip-up he goes back to calling it a her. However, it is shown that FitzRoyce has little regard for the shark, and likely doesn't care one way or the other about its gender.
A "mother" shark would not have tried to find or protect her baby. Sharks do not care for their babies after they are born. In fact, they have been known to eat their young. The MOST they will do is to search for a safe place where they can lay their eggs or give birth. However, it is never once said that the shark is protecting its baby.
At the start we overhear that there are four pressurized viewing tunnels at 40 ft under the surface. However, we see no isolation chambers at the entrance, nor do we see any decompression stations or stages which would be necessary because anyone staying pressurized at 40 ft. would require decompression staging after approximately two hours of being in the control room or viewing tunnels, yet workers pass freely between the surface and pressurized sections during the movie. However, just because we aren't explicitly shown this happening, does not mean that it never happens.
The movie was filmed, and takes place in SeaWorld in Orlando, Florida. Not only is Orlando, Florida 50 miles from the Atlantic Ocean, but at the time SeaWorld was surrounded by hotels, office buildings and residential neighborhoods. However, it is never actually said exactly where the movie takes place.
Sean and Michael Brody appear to be older than their characters were in the first and second movies. In the original movie, Michael was about 12 years old and Sean was 3 or 4. In Jaws 3, Michael appears to be 29-30, while Sean is between 19-21. Part 3 takes place 9 years after the events of part 1. Michael should only be about 21 and Sean around 13 years old. However, the exact year the movie takes place is never said.
The front of a submersible seems to vanish briefly as it rotates. The sub model clearly reflected the color of the special effects background (a greenscreen or something similar) and got "keyed out" when the underwater footage was added.
When the shark is heading for the control room it is not swimming - the tail is perfectly still. It also comes to a complete stop when it breaks the "glass" instead of pushing through due to momentum.
When the first shark hits the lagoon gate, its head noticeably compresses about 6 inches into its fake body.
Monafilament strings hold up "waving" flags and the harpoon that Mike Brody fires at the shark.
Throughout the movie, a stream of air bubbles escapes from the shark's dorsal fin.
When Kathryn and Mike go to get into the submersible to go investigate, both are in wet-suits. Kathryn's hair is soaked like she just got out of the water but hasn't entered the submersible yet.
The men breaking into the park exchange several lines without moving their lips.
Different voice actors dubbed Dan's voice throughout the film.
As the tour guide tries to lead the tourists out of the "Undersea Tunnel", the green screen stage outside the tunnel set is clearly visible (full-screen version).
Sharks should always be transported submerged in water, not wet-wrapped and transported on a sling. They need water to pass through the mouth or over the gills to breathe. The hoist in from the roof meant leaving him out of the water far too long for such a delicate shark. This is a newborn shark that would've died much sooner under these stressful conditions.
The baby shark is kept in a viewing pool with opaque stone walls about three feet high and no surrounding guardrails. This is problematic for two reasons. First, it's impossible to see the shark unless it comes to the surface -- and sharks spend almost all of their time underwater. Second, with viewers standing this close, a visitor could accidentally get his or her hand bitten off. No theme park or zoo of any repute would ever allow such an inept design for a dangerous animal on display.
Mike and four other guys go out on the boat to help free the people trapped in the under water tunnel. When Mike goes under water he goes down alone, while the other four stay on the boat. After FitzRoyce is killed by the shark we see these four standing on the boat as Mike welds the tunnel below. When we see Mike under water there is now another diver down there with him working on the tunnel. When Kathy joins Mike this diver returns to the surface. Then when Calvin tells them to bring them up after the shark got free, there are still the same four on the boat and not the diver who just came up. So where did this other diver come from and where did he go?
How is it that the people in boats were able to get to the water skiers and rescue them when the shark was pretty much right on their heels , at least one if not more should have been attacked right away .
In the final act as Mike Brody (Dennis Quaid) & Dr. Morgan (Bess Armstrong) surface after defeating the shark, she asks about "the others" safety for which Quaid responds, "Calvin made it -- [and] Lisa!" Referring to Ethel from the control room played by Liza Maurer.
Near the beginning of the movie, when Overman's girlfriend shows up to throw his belongings at Brody the passport which contains his driving license and credit cards has the actor's picture. however as it opens one can see that it is actually issued to a Mary Ann Chalmers with a birth date in 1952. It says she lived in New Hampshire and that the passport had expired in 1977 long before the movie had even been made.
When the mother shark escapes the filtration pipe and attacks Brody and Kay, Brody later asks "How the Hell did he get loose?" He says "he" despite knowing that it's a female shark.