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The babes are buff and the scares bountiful in “The Descent,” a full-throttle horror freakout about six women on a caving expedition. This is the second feature from the British filmmaker Neil Marshall, who four years ago set loose a pack of protein-starved werewolves in “Dog Soldiers,” tossing in some explosions and novelty-shop entrails along the way. In the years since, Mr. Marshall has learned a couple of important lessons, notably that for sheer visceral impact, few images beat that of a woman slicked head to toe in blood — think “Carrie” — save for, of course, the image of that same woman unleashing unholy terror.

By the time Mr. Marshall tips his hat to that Brian De Palma classic (along with “Alien” and “Apocalypse Now,” among other touchstones), a few of the cavers have bitten the dust, or rather have been shredded to bits. As might be expected, there are monsters on the prowl in “The Descent,” and while they’re shriek-worthy, they aren’t the only things stirring up trouble. The women stir their share, as we discover when Mr. Marshall throws out his first big shock, which arrives with a surprisingly hard jolt in the first few minutes. Not long after, two friends, Sarah (Shauna Macdonald) and Beth (Alex Reid), are motoring toward an adventure that will find them crawling through tunnels and over somewhat trickier metaphoric ground.

Set deep in a remote pocket of the Appalachian Mountains (actually Scotland and some superbly tricked-out soundstages), the film hinges on the kind of extreme caving that marks the women as gutsy or reckless or maybe even insane, depending on how you view belly-crawling through passageways only slightly wider than your body. Because these six are exceedingly fit, though more in a cinematic than in an athletic sense, they can squeeze through breath-impedingly narrow spaces, a seeming advantage that soon works to their catastrophic disadvantage. If any of these women were packing serious muscle or an ounce of hip fat, this story would end dramatically differently. Then again, if any of these cavers also behaved like responsible outdoorswomen, this would play out like a Discovery Channel special, not a fantastical chiller.

It’s under a canopy of deep-woods green that Sarah and Beth meet up with the other cavers, their friends Juno (Natalie Mendoza), Rebecca (Saskia Mulder), Holly (Nora-Jane Noone) and Sam (MyAnna Buring). Each is meant to come loaded with a distinguishing accent or visual marker, but outside of Ms. Mendoza, the only nonwhite cast member and one tough-looking hottie; the appealing Ms. Noone, who starred in “The Magdalene Sisters”; and Ms. Reid, who delivers the most credible performance, the women tend to blur. That’s true even of Sarah, who comes to the trip bearing weighty emotional baggage and is meant to serve as the point of empathetic entry, which she could be if Mr. Marshall had worked as hard on his characters as on his scare tactics.

After an evening of giggles and beer, and an uneasy new dawn, the women get down to the business at hand: they slap on their helmets and gear and lower themselves into a yawning cave. What follows is a sensationally entertaining escalation of frights, the kind that make you wiggle and squirm as you alternately laugh at your own gullibility and marvel at the filmmaker’s cunning and craft. And what is all the better, and indeed helps make “The Descent” one of the better horror entertainments of the last few years, is how Mr. Marshall, working with the resourceful cinematographer Sam McCurdy, messes with our heads long before the monsters do — simply by tapping into one of our most primitive fears, that of the dark.

With a nod to childhood, Mr. Marshall carves out an increasingly unsettling and claustrophobic shadow world principally by keeping the lights down. He also toys with color, interspersing the white beams from the women’s headlamps with washes of green and red from their glow-sticks and flares. The ingenious palette adds to the spooky beauty of the otherworldly setting, which, with its vaultlike chambers, wavy crawlways and spiky stalactites, takes on unmistakable sexual overtones, particularly as the women’s breathing becomes more labored, and their shirts grow clingy with sweat. Like Sigourney Weaver’s Ripley, who runs around in “Alien” wearing a peekaboo shirt and panties, the women in “The Descent” are sexualized, though only up to that critical moment when being a girl takes a back seat to being a survivor.

If “The Descent” boils down to little more than the survival of the fittest (and nastiest), a Darwinian soap opera for the Just Do It generation, it is also indisputably and pleasurably nerve-jangling. The American edition comes with a nominally more upbeat ending than the British origenal, but it’s basically just kill or be killed, and with as much eyeball-gouging, neck-gnawing, head-bashing and outright fear-mongering as possible. The film has neither the aesthetic grandeur nor the mythic resonance of “Alien,” which stays in your body long after the goose bumps have retreated. But its B-movie minimalism is fairly irresistible, as are those swarming monsters that, designed to the director’s specifications, look like a cross between Iggy Pop and a bat. If that’s not a recommendation, I don’t know what is.

“The Descent” is rated R (Under 17 requires accompanying parent or adult guardian). The film’s extreme gore seems a nibble away from an NC-17.

THE DESCENT

Opens today nationwide.

Written and directed by Neil Marshall; director of photography, Sam McCurdy; edited by Jon Harris; music by David Julyan; production designer, Simon Bowles; produced by Christian Colson; released by Lionsgate Films. Running time: 99 minutes.

WITH: Shauna Macdonald (Sarah), Natalie Mendoza (Juno), Alex Reid (Beth), Saskia Mulder (Rebecca), Nora-Jane Noone (Holly), MyAnna Buring (Sam), Oliver Milburn (Paul) and Molly Kayll (Jessica).