Goofs

The size of the sharktopus, and especially the length of its tentacles, varies from scene to scene. Generally it tends to get larger and they tend to get longer.

While on the boat, Nathan Sands (Eric Roberts) shouts "Dock this thing" and takes over the helm. The next scene shows the boat continuing to head directly away from land.

When Andy shoots at the sharktopus to distract it from the reporter, he uses a machine gun. It shows him shooting the gun and the next scene is his gun's bullets bouncing off of the ship and the sharktopus. A second later, the scene shows Andy without a gun in sight.

When the guy is swimming face up in the pool, he is shown without anything on his head and begins to swim toward the surface. When he is shown coming out of the water, he is wearing a sombrero.

After the sharktopus slits Nathan's throat, the blood disappears as he falls to the floor. It then reappears after it is cut from Andy regaining consciousness after being knocked unconscious by the sharktopus, before Nicole rushes to her father.

The sharktopus has an octopus' tentacles in the place of a shark's tail fin. An octopus swims using a siphon under its head, not with its tentacles (which are used for crawling on the ocean floor). The sharktopus, therefore, lacks a means of propulsion through the water.

Early exposition in the film claims that the sharktopus is being used by the Navy (presumably the U.S. Navy, given the uniform of the speaker) to go after drug runners. Chasing drug runners is the responsibility of the U.S. Coast Guard, not the U.S. Navy.

The sharktopus frequently attacks swimmers from close to shore in water that should be too shallow for it to hide its admittedly inconsistent size.

Octopuses use their tentacles for grabbing things, not stabbing them with non-existent spear-like points like the ones that the sharktopus has.

The sharktopus makes numerous noises, including roaring and squealing. Sharks have no organs for producing sound, and only one shark species (the draughtsboard shark (Cephaloscyllium isabellum) from New Zealand) is known to be capable of producing any kind of sound.

None of the things the Navy Commander says in the film are accurate for U.S. military (Department of Defense) research or development projects. No one person has the authority to do the things which this character does or claims to be able to do (expand a contract, cancel a contract, modify testing, approve changes, etc.).

Though the sharktopus is female, it is mistakenly addressed as a male.

The term "octopi" is used as the plural of "octopus". Pez, and especially Nicole, would know that the correct term is "octopodes". This is a very common mistake, as "octopodes" is rarely used nowadays and "octopi" is only thought to be the plural because people do not realize that the word "octopus" is derived from Greek, not Latin.