In theaters

MARCH OF THE PENGUINS, directed by Luc Jacquet, written by Jordan Roberts, 80 minutes, rated G.

It’s their bodies that you notice first.

Not made for flying, not particularly well made for walking, the emperor penguins of the Antarctic are awkwardly built, their rotund heft, stunted limbs and gnarled feet creating a curious waddle that’s at once comical and endearing.

It’s only when they swim in the freezing waters of the Antarctic that these beautiful creatures realize a ballet of physical release that seems beyond their capabilities.

There, in the electric blue of a faraway deep, they become tuxedoed missiles – as slick as dolphins, as graceful as seals, faster than you could imagine, able to dart with ease to the feast of fish that fret along the fringes of the icebergs that sustain them.

Still, on land, where these penguins spend most of their lives, they are designed in ways that appear completely wrong for the process that takes up so much of their lives – breeding.

Pegged to a life of almost impossible difficulty, these driven, nearly 4-foot-tall birds must walk more than 70 miles through the most treacherous terrain and weather in order to come to a place in which they feel safe to hatch their chicks.

And then, to find food, they must walk those 70 miles again. And again. And again. Meanwhile, starvation is a thief that has its way with them.

It’s this moving journey – the lives that spring from it, those that fall because of it – that is the focus of Luc Jacquet’s excellent, often harrowing documentary, “March of the Penguins. “It’s one of the finest films of the summer and likely a contender for Best Documentary when the Academy nominates next February.

Narrated by Morgan Freeman in a knowing voice that delivers the highs and lows of this journey without a trace of excitement – respect is what he achieves – the film is being billed as a love story, which it is. “Like most love stories, it’s about an act of utter foolishness,” Freeman says, referring to the lengths in which these birds will go to ensure the survival of their young.

Sadly, some won’t survive.

Following the penguins over the course of a year, director Jacquet chronicles a quest that finds the birds facing death daily in an effort to sustain life. If that sounds ironic, nature and instinct could care less. Bonded by this native pull, the birds – thousands of them – push through a sort of hell in which the temperature averages 58 degrees below zero. And that’s without the wind chill.

Blizzards strike. Water is sparse, but for the resourceful bird, it can be found after the storms in pellets of snow. When the exhausted females leave for the ocean to find food, the males are left behind for two months to balance the egg on their hooked feet. Huddled together for warmth, a fold of their belly fat protecting the egg from the elements, they must somehow keep moving lest they freeze themselves.

There is no food for them, just patience, hardship, endurance. Should the egg touch the frozen surface, it will freeze in seconds and life will be lost. And so they can’t drop it – though some accidentally do. It’s the wail of disappointment and grief that rings from their throats that binds us to them – just as it does when the females return to either see their hatched chicks for the first time, or to realize that in their absence, their mate failed to keep the egg safe.

In the Antarctic, where the southern lights weave through the skies like hallucinogenic ribbons, the emperor penguins endure.

Grade: A

On video and DVD

SIN CITY, directed by Frank Miller and Robert Rodriguez, written by Miller, 124 minutes, rated R.

The blistering potboiler “Sin City” is infused with high-end style – shadowy, black-and-white cinematography shot through with flashes of color set against the dreariest of worlds. The look is sexy and disarming, often beautiful and then, in an instant, drop-dead ugly. The good news? None of it comes at the expense of substance.

As directed by Frank Miller and Robert Rodriguez from Miller’s popular series of graphic novels, this violent, sometimes boldly funny film taps into the meanest of genres – the hard-boiled detective novel and pulp fiction, which enjoyed their heyday from 1920 to 1950 – and the film noir movement they inspired.

With great panache and a broad wink at its audience, “Sin City” cranks up the heat and dices up the double talk. In its grit, it rivals the outlaw toughness of the Western, which influences it. In its darkness, it echoes the Gothic, which deepens it. Like jazz, the movie is distinctly American, an exciting, fresh blast of moviemaking that’s urban and racy, with dialogue that snaps with an undercurrent of sleaze.

Three stories hold this dark gangster flick together -“Yellow Bastard,” “The Hard Goodbye” and “The Big Fat Kill.” All are a nonlinear rush, so it’s best to go to the film without any preconceived notions of what it is.

Trust Miller, Rodriguez and guest director Quentin Tarantino to take care of you. There will be plenty to look at along the way, starting with the excellent cast, which includes Bruce Willis, Clive Owen, Benecio Del Toro, Brittany Murphy, Rosario Dawson and an almost unrecognizable Mickey Rourke in the comeback role to beat this year. The stories they inhabit are too detailed to fully explore here, so we’ll leave it at this: each story concerns itself with the state of the world’s rotting underbelly, a seething infestation of crooks and other vermin that needs a good cleaning.

It gets one, too, but not before heads fly and limbs are lopped.

Grade: A-

Christopher Smith is the Bangor Daily News film critic. His reviews appear Mondays in Discovering, Fridays in Happening, Weekends in Television, and are archived at RottenTomatoes.com. He may be reached at BDNFilm1@aol.com.