These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: The SNES Waterworld game is known as a pretty bad game. However its OST by Dean Evans has a lot of awesome tracks.
Diving is a perfect example of an amazing ambient track on this OST.
Designated Hero: The Mariner. Though it's more Anti-Hero with shades of trying to avoid The Call through most of the movie.
Ensemble Darkhorse: Dennis Hopper seems to be having a great time playing the villainous Deacon. As such, he's one of the most enjoyable parts of the movie.
Ham and Cheese: Depending on your opinion of the movie, Dennis Hopper may qualify.
Narm: The scene where Kevin Costner blows up at the kid over the crayons. The scene where Helen screams "FOOD!" also qualifies. The sentence it's a part of isn't actually that bad, but the fact that she just randomly screams the last word makes it all fall apart.
And there's the infamous "My boat".
Older Than They Think: The setting has more than a few similiarities to the French comic series Aquablue.
Kevin Costner throws her in the ocean and she can't swim. Please, oh God, leave her...
What an Idiot: Your world has been completely submerged in water, and you've found a man who can breathe underwater and has various other aquatic abilities. Do you A) make use of these talents or B) try to kill him for the horrible crime of having gills? In Waterworld, the answer is B.