Sports documentaries can’t just float. At some point they also have to dig. As beautiful as the cascading ocean wave might be, as majestic as the slow-motion buzzer-beater may seem, there has to be something more to a feature-length film than the photo op.

Mark Obenhaus’s “Steep” is the latest in a long line of sports documentaries that fail to deliver anything more than these superficial wonders. It’s unable to offer any firm understanding of the pageantry, psychology, or physiology inherent in its sport of interest: extreme skiing. What sets it apart, however, is yet a more profound failing — namely its inability to get even the sports stuff right, never once putting us inside the head or heart of the competitor.

The goal of “Steep” is advocacy, to promote a sport that’s still in its relative infancy. As one extreme athlete after another is plopped in front of the camera and asked basically to declare how cool it is to be airlifted to the summit of a mountain and to plunge down hundreds and thousands of feet in a barely controlled descent, “Steep” ignores examining the dangers, the rush, or the launchpad to minor celebrity that seem integral to its popularity.

The closest we get is a segment that chronicles the geography of the sport and its ever-shifting hot zone. Initially, it was the mountains of Europe that drew the thrill-seekers and daredevils, who would live there year-round in constant search of a death-defying fix. Today, the allure has shifted to the wilds of Alaska. Flying in via helicopter across terrain that no human has disturbed for years, decades, or longer, the skiers are lifted to the peaks and plunge downward through never-before-skied powder and over uncharted dangers.

For all the film’s blunders, this is the one story that “Steep” seems to have right: the way that it isn’t the verticality or the remoteness of the mountain that matters, but the allure of the unexplored and untouched that seems to drive these men (it seems to be a sport made up entirely of males) forward.

Woefully absent from the conversation is a serious evaluation of the price that is paid to play. What has the death toll been? We know it’s at least one, because one of the movie’s central subjects perishes on the slopes during production. More to the point: What mental state drives people to do this? Is it a death wish? A need to explore? A rush that can’t be found elsewhere? “Steep” leaves you with more questions than answers.

Apart from the thrill, part of the draw seems to be a simple grab for fame, which somehow puts the incredible dangers in stark relief. Almost all of the extreme skiers here talk eagerly of their idols, chief among them Bill Briggs, who in 1971 skied the Grand Tetons, the event many point to as the birth of extreme skiing. Almost everyone interviewed says he came to embrace the sport by watching VHS recordings of the extreme stunts. As these younger skiers make their own extreme videos, it is no doubt an attempt to do on YouTube and DVD what those earlier death defiers did on magnetic tape.

It’s unfortunate Mr. Obenhaus brushes by this material, relegating the social dynamics to mere footnotes. But it’s nothing short of maddening that he is incapable of putting the viewer in the boots or in the minds of these fearless freefallers. Watching jumps from afar, often with the camera on a helicopter, or watching grainy VHS copies of the old greats, we lack the basic vantage point of the experience.

A few years ago, the surfing documentary “Step Into Liquid” was another shallow disappointment of a sports documentary. But what buoyed it for surfing fans was some of the most amazing surfing footage imaginable, with the cameraman riding mere inches from the board before crashing into the froth. “Steep” almost entirely lacks this “wow” factor. Its single most amazing stunt — a guy who starts a jump while skiing and ends it on the end of a parachute — doesn’t take place on a mountain at all, but in a sequence filmed over a river.

There’s a captivating film to be made about the world of extreme skiing, and one of these days a director is going to make it.

ssnyder@nysun.com