TEN years ago, Kevin Costner's career took a turn for the worse when he made a hugely expensive film called ''Waterworld.'' Since then, the film has become synonymous with megalomania, hubris and all the other fancy words that journalists like to use when things fall apart and the center will not hold. But unlike his other movies ''Wyatt Earp'' and ''The Postman,'' which are really bad, ''Waterworld'' is simply a dumb, expensive dud, not an epic, studio-imploding disaster on the order of ''Heaven's Gate'' or ''Battlefield Earth.'' If you are in the market for a truly horrendous movie, one of...