Corrected entry: The Mariner takes Helen down to the sea bed in a makeshift 'diving bell'. He tells Helen there is only enough air for one person. The depth they dive to is shown as quite comfortably exceeding 200m. (To save this turning into a science essay I'll include this link: http://en.wikipedia.org/wiki/Boyle's_law). Regardless of suspension of disbelief, there is no way that a bell of that size would carry enough air for even one person at that depth for that long. There's also the matter of decompression stops when they return to the surface. The Mariner wouldn't need them but Helen certainly would. It could be argued that the deco stops occurred off-screen and the audience doesn't see every second of their trip. Fair enough however The Mariner has no depth gauge. That would also assume he is not only aware of decompression as a concept, but is familiar with a specific set of decompression tables and schedules, to the point of having them memorised on the off chance he ever takes a human diving. Highly implausible.
Corrected entry: The Exxon Valdez is designed to carry crude oil. Crude has to be refined into higher octane products to be used in jet skis, automobiles, etc. The refining process is difficult and requires large amounts of power. It would be impossible to do on the tanker itself. And it is extremely unlikely that the smokers would have come across high octane products on another ship. They tend to be refined near to their consumers and not shipped around.
Corrected entry: How far ahead in the future are we anyway? Hundreds or maybe thousands of years? Do you know how long tankers like that can stay at sea? Twenty or thirty years at the most. That's a rather short time for everyone to forget about dry land.
Corrected entry: Where do the smokers get their cigarettes from? Cigarettes do not have an indefinite shelf life. The tobacco will dry out after just a few months and after a few years they would crumble away. Given that the smokers certainly don't have the capacity to grow tobacco or manufacture cigarettes, and the cigarettes they are smoking could not have survived since the global disaster that caused the sea to rise, there shouldn't be any around.
Corrected entry: If it has been so long since the water levels rose that no one remembers a time when dry land was above water, how did the little girl come to have such an accurate map to it tattooed on her back?
Corrected entry: If Kevin Costner's character has gills, and can breathe under water, why would he have a device for someone else to breathe underwater? He very states that he is a loner, and does not travel any way but alone. I can see building one after he picks up his extra passengers, but beforehand doesn't make since.Jazetopher
Corrected entry: Featuring the Exxon Valdez in the movie is a nice piece of social commentary. However, when the real Exxon Valdez was repaired and placed back into service after the Prince William Sound disaster in 1989, it was rechristened the Sea River Mediterranean.
Corrected entry: It is a known scientific fact that a planet without land will create waves rising from 500 to a thousand feet. This is because there is no land that can break the waves' rise. This would make the surface uninhabitable by any man-made structure or vessel especially with Waterworld's current human technology. Waterworld barely has any waves.
Corrected entry: It doesn't make sense that the Smokers have so many shells. In the Atoll Assault scene the four-barreled machine gun chassis is dumping out about 50 shells every 4 seconds.
Corrected entry: Since all the Jet Skis in the movie seem to be from the late twentieth/early twenty-first century, and the Exxon Valdez can only hold so much oil, and it has probably been centuries (at least) since the water level rose, there would probably be a very strict oil rationing law in place for there to be any oil left at all. Certainly not enough for the villains to be as profligate with the use of the Jet Skis as they are.
Corrected entry: Can anyone explain to me why the Exxon Valdez, an oil tanker that ran aground at one point, is still afloat, yet there is no sign of any military ships (except the sunken submarine). Military ships tend to be more "sink-proof" than civilian ones.
Corrected entry: At the end when the three jet-skis are about to crash, the explosion goes off a bit too early.
Corrected entry: When the mariner questions the woman about the little girl's drawings, she says "she's like a mirror, she draws what she sees." Later she claims the mariner "has things no one else has seen" like "that reflective glass". What do you think a mirror is, woman? And why do they have "normal glass" and not "reflective glass"?
Corrected entry: Wouldn't the Jet-Ski's be useless as there wouldn't be any fuel available for them if all the land is flooded in water?
Corrected entry: At one point, the mariner trades a handful of dirt for water and a potted plant that has more dirt in it than he originally traded.
Corrected entry: Right at the beginning Costner uses a machine to convert his urine into drinkable water. Any machine which can make urine drinkable would work perfectly well on seawater. Urine has far more contaminants than seawater.
Corrected entry: At the end of the movie, when Costner and friends do find land, it turns out to be Mt. Everest. This establishes the sea level at that time. Using that and going back to the middle of the movie, we see Costner diving into the ruins of a city where skyscrapers are evident. The tallest skyscraper is approximately 1800 feet high, which would leave a difference of, say, 4 miles underwater. It would be pitch black at that depth and the water pressure would kill a human that far down, gills or no gills.
Corrected entry: Paper is seemingly a rare commodity in Waterworld, but all the bad guys run around smoking cigarettes all the time.
Corrected entry: Can planes, boats and jet-skis run on plain crude oil? There's no real petrol ever mentioned.