Continuity mistake: After the mariner escapes the atoll and begins turning the gunboat towards the deacon, we see the firing path pass the end of the atoll wall. A couple shots later, it shows four smokers on jet skis getting shot as they exit the main gate, which is in the center of the wall facing the attack and had already been passed by the firing path. (00:38:00)Jason Sieberg
Revealing mistake: The Mariner had just been ignominiously catapulted off the mast of his boat as a result of the tethering rope breaking loose from the circling airplane. In the scene showing him climbing back onto his boat land can plainly be seen on the right side of the frame. This occurs just prior to Helen saying: "Oh, I'm really sorry". (00:57:25)MartyS
Revealing mistake: When escaping the Smokers for the third time, the Mariner picks up Enola and swings to the other side of the boat with a rope. But you can see a second rope going down behind Costner's back. At the ''handle'', it's tied up with the one Costner is actually holding on to. (01:18:25)Friso94
Factual error: Regardless of the type of event that caused the ice caps to melt, Waterworld, as shown, is impossible because: A. Scientists have measured that if all landlocked ice (Antarctica, Greenland, and the like) melted, the worldwide water level would not rise by anywhere near enough to cover the whole world in water. B. The melting of the North Pole ice cap would have no effect at all on the worldwide water level because that ice cap is already floating in the water (try putting an ice cube in a glass of water and letting it melt. The water level won't change). C. Unless the event that caused the ice to melt also altered the earth's tilt, the poles would still be cold and would refreeze, lowering the water level.Grumpy Scot
Continuity mistake: In the beginning when Mariner goes diving off his boat for sunken treasure, he fills a timer with a handful of small stones which steadily drop to bring up the diving equipment when exhausted. After the camera shows some scenes to imply time going by, you can clearly see the amount of stones fallen is equal to about ten handfuls of stones.
Factual error: When Costner spots the Smokers on their jet skis, his catamaran has no sails up and is dead in the water. He hastily puts up the sails and speeds away, outrunning the Smokers. This would be impossible in real life, from a standing start and light wind.
Factual error: The Mariner's gills that allow him to apparently breathe ocean water, are extremely unlikely. Even mammals that live underwater, like whales and dolphins, did not evolve gills. It is not possible for a warm-blooded creature to supply itself with enough oxygen using only small gills.wizard_of_gore
Continuity mistake: When Mariner is knocked into the mud pit while in the cage we see that it does indeed sink. However as the woman and the girl are crossing the bridge to get to the windmill, the camera cuts to Mariner in the cage. The cage has sunk so that he only has room for his head and shoulders. Then as the woman and girl run past him there is another shot in which the cage is now further out of the mud and Mariner has room for the majority of his upper body.Scrappy
Continuity mistake: After the Mariner rescued Enola, the Deacon and his goons collide. As the fireball of their collision comes up, their wakes are still visible. A second later, the fireball is still growing but the wakes have totally subsided. Not possible given the explosion is only several seconds old.Movie Nut
Continuity mistake: Near the end one of the balloon's ropes is shot, causing the girl to fall in the water. Yet, seconds later as they float off all 6 ropes are holding the basket up, uncut.