While Waterworld isn't good by any stretch of the imagination, if you are playing a "location of the week" type game (say you were a Time Travelling Hobo type character), it's perfectly ok a background for that game, and provides plenty of material for it.
Quite a lot of not-great-but-visual films make for good "Time Travel Box Arrives and goodness the entire place is water..." adventures.
"If you solve our faction based problem with the sonic death wielding half fish people we will use our dredging machines to find your Delorean and drain it out"
"What is your issue with the sonic death wielding half fish people"
"They want us to watch the War Between The Land and the Sea all the way to the end"
"I'm afraid I can't help you, I live here now"