Amusing more than frightening, gross more than engrossing, “Final Destination 3” delivers only what its two predecessors promise: absurdly complicated, “accidental” deaths that shock viewers and characters alike. Everything else attempted — plot, characterization, logic — merely serves to skimpily connect one corpse to another and add screen time. The result, overall, is a pathetic film punctuated by moments of disturbingly entertaining slaughter.

Predictably, “Final Destination 3” opens with its tensest scene of destruction — this time in the form of a roller-coaster catastrophe. A group of high school students aboard the “Devil’s Flight” collide with fate and hard steel as their delicate bodies are ejected from their seats and then plummet, soar, or pin-ball toward a painful, messy death.

But, of course, before this actually happens, high-school heroine Wendy Christensen (Mary Elizabeth Winstead) foresees it all in time to panic, save a few lives and then see her predictions reach devastating fruition. Wendy’s sudden endowment with precognitive powers, among other supernatural occurrences, is never explained, but she emerges as the film’s Tiresian prophet — gifted with predicting the future, but powerless to change it.

With the deaths of boyfriend and best gal pal on her conscience, Wendy despairingly realizes that everyone who had originally boarded “Devil’s Flight” is now at the mercy of a cruel, creative Grim Reaper. And as they begin to die in implausible ways, like being burned alive in a tanning bed or receiving multiple head-wounds from a nail-gun, Wendy seeks help in convincing the doomed that their days, or minutes, are numbered. Much good may it do them.

She teams up with Kevin (Ryan Merriman), the flirty meathead who was luckily saved from riding “Devil’s Flight,” but acts as if he wants to ride Wendy, and together they try to map out a method to fate’s madness. Together they conclude that the ordering of the deaths corresponds to seat number on the coaster. Originally seated in the back, Wendy and Kevin have the most life to live, so they rush from one place to another trying to save whom they can, but their time runs out with every head that pops.

As traumatic as all this sounds, the characters seem to think otherwise. The hurried pace of the narrative and poor acting impose an attitude of unrealistic indifference to Wendy and Kevin, who, instead of committing themselves to a mental institution, choose to witness their friends’ horrible deaths without sincere concern. Their forewarnings are as half-hearted as they are inane. No wonder no one believes them.

It is actually quite funny to see them unsuccessfully try to prevent what everyone in the audience knows is coming. And while laughing might otherwise be considered inappropriate in a film so macabre, the feather-weight treatment of heavy material turns it into a travesty worth giggling over. Examples include, but certainly aren’t limited to, one character’s description of his boss as “Osama bin Supervisor,” or Kevin’s sudden confession that before his Berkeley-bound girlfriend perished via roller coaster, he thought of proposing marriage. Phew!

In a film like this, no one expects the characters to resemble real people, not even real high school students, and they do not. From their curiously absent parents to their pretentious “Creek”-ian dialogue about the philosophy of their made-up world, nothing about them even approaches verisimilitude, with the exception of one thing: their appearance. Removing eye-candy from a horror movie is a huge misstep, and the biggest disappointment of “Final Destination 3.” Throughout most of the film, Wendy looks like a walking mascara smear, while Ryan Merriman resembles a chubby, overgrown fourth-grader. Even the four naked breasts that appear in the tanning bed scene invite comparisons to lumpectomy patients. The rest of the cast — either over- or under-built, over- or under-bronzed — just comes too close to looking like Harvard pre-meds to create a pleasurable viewing experience.

While it could have been one hell of a roller coaster, “Final Destination 3” is more of a distorted, fun-house reflection of a suspense thriller. Whether by grotesquely inflating fatalistic themes, or by thinning out its best moments with a spiritless plot, director James Wong finishes off the “Final Destination” trilogy with the most unsatisfying of the three films. If only he had stopped at Devon Sawa.