“Piranha 3DD” is a textbook case of low-aimers confusing camp with cornball excess, in which an audience expecting silly thrills is subjected to nonsensical ramblings that bear no weight towards humor or amusement. If only there was some sense of irony to underline that prospect, but no such luck; those standing behind the camera are looking on here with deadpan conviction, perfectly content in the realization that they are in this, more or less, for financial benefit. I despise the very idea of that motive – it is an abuse of the medium, a counter-culture impulse in the guise of innocent entertainment at a time when the Hollywood machine needs less cattle and more instigators. We could at least have a good time, however disposable, at a film that ebbs low if it aims there, or at least contains some sample of wry awareness. Think of “Snakes on a Plane” as an example. But a movie this shameless, this grotesque in its assessment, only permeates the desperation of the mindless grab. Earlier incarnations of the “Piranha” franchise – including a remake that precedes this one – knew they were about the stupid possibilities of the genre and enjoyed reveling in the exercise. Here is a follow-up that could not be any more clueless if it had been conceived in a void.