Waterworld is set in the 21st century, a time when polar ice caps have melted and flooded the continents of the Earth. Humans survive via floating communities called atolls that are made from scraps of metal and recycled sea vessels. After a long time, humans have eventually forgotten what it’s like to live on land. Instead, they formulated some myth regarding a place called “Dryland” that can be found somewhere in the vast ocean.
Five hundred years after the meltdown, a man called “the Mariner” arrives at one of the atolls. The man intends to trade dirt, a highly valuable goods used for growing plants. When the residents of the atoll find out that the mariner has gills and webbed feet, they become afraid of him and they decide to drown him in a brine pool. Before the people can kill the mariner, pirates known as the Smokers arrive in the community. The pirates are looking for an orphan named Enola, who has a map leading to Dryland inked on her back. The Smokers’ leader, a man called “the Deacon,” wants to be the first man to reach Dryland and build a city on it.
On the other hand, Enola and her guardian Helen, formulate a plan to leave the atoll with an inventor named Gregor. Their plan crumbles to dust when Gregor accidentally releases the gas balloon that they would have used during their escape. Before the Smokers can overwhelm the whole atoll, Helen saves the mariner from drowning when the latter promises to help them escape using his vessel.
During their journey, conflicts arises when Helen damages the mariner’s boat. On one side, Helen presses the mariner to tell her where he gets his dirt. Using a diving bell, the mariner brings her to a now water submerged Denver where he scavenges for dirt and other scrap materials. It dawns on Helen that the former human civilizations have certainly lived on lands before.
After that, the mariner and Helen are snatched by the Smokers and they are used to bring out Enola. They dive into the water in order to escape. Underwater, the mariner uses his gills to share oxygen to Helen. When they break out the water’s surface, they find the mariner’s vessel in utter wreckage and there’s nobody around. Fortunately, Gregor comes to rescue them and with him, they band with the survivors from the atoll attacked by the Smokers.
The Mariner follows the pirates and finds them celebrating their new found map on the remains of a sea vessel. With a flare in his hand, the Mariner threatens the Deacon and his crew that he will burn the rest of the ship if they do not hand over Enola. The Deacon does not believe him and to his surprise, the Mariner drops the flare on the oil tank reserve and the ship explodes. As the ship begins to sink, the Mariner escapes to Gregor’s balloon with Enola in tow.
The Deacon manages to grab the rope of the balloon but Helen throws a bottle at him. As he falls down, he draws out a gun and shoots at the balloon. A bullet grazes one of the lines causing Enola to fall. The rest of the Smokers converge on the spot where Enola lands. Upon seeing this, the Mariner ties a rope around his ankle and jumps. He grabs Enola just in time and both propels back to the balloon’s safety.
Using an old China Airlines magazines, Gregor interprets the symbols on the map. They head for the location indicated and they reach Dryland. Dryland turns out to be Mount Everest, now filled with greeneries and abundant with wildlife. The group set foot on the ground and they find the remains of Enola’s parents in a hut that they have passed by. The Mariner then leaves them as he deems the ocean as his only home. The movie ends with Helen baptizing him as “Ulysses.”