Not long ago, I saw a documentary about sharks in the wild. The male bites the frisky female on her flank, both to show his interest and to subdue her as he attempts penetration. Initially the female resists; one was filmed wriggling free of a series of circling males until she becomes exhausted and an alpha male has his way with her.

According to the narrator, shark reproduction favors the most powerful males and strongest females. Over time, the female evolves tougher skin to endure, or perhaps elude, the male love bite.

If that’s what happens in the open sea, what must it be like in tighter quarters?

“Equity,” an intelligent and enthralling thriller set in a shark tank of New York investment bankers, hedge-fund executives and tech entrepreneurs, imagines just that.

The film, directed by Meera Menon and written by Amy Fox, is as ruthless and hypnotic a study of a cutthroat species as the documentary I saw about the carnivorous fish. Maybe it is even more so, as it is a story of alpha females, as well as males.

This female-driven production about driven females stars Anna Gunn (“Breaking Bad”) as banker Naomi Bishop, the firm rainmaker lately experiencing a drought. Sarah Megan Thomas is Erin Manning, her assistant, and Alysia Reiner (“Orange Is the New Black”) plays Samantha, an assistant U.S. attorney investigating Gunn’s firm. That storyline provides one of the plot’s conflicts. Another is that banker and assistant each want promotions and are denied.

At the outset, it’s hard to like Naomi. She announces herself as the female Gordon Gekko (the character Michael Douglas played in “Wall Street”). While he exhorted that “greed is good,” she forthrightly admits that she “likes money.” She likes the numbers, likes the adrenaline rush of risking it on a new venture and, most of all, she likes the power it represents.

She makes few concessions to femininity and none to glamor. Her body is womanly, rather than girlish, her clothes purely functional. Naomi lets off steam by slipping into boxing gloves and taking the stuffing out of the punching bag. She is in control of her emotions.

At the outset, it’s easy to like Erin and Samantha, both model-slim and flirty (even though both are married). From Erin’s perspective, Naomi is the boss from hell. From Samantha’s, the banker is insufficiently idealistic. “Equity” asks us at first to align with the younger women because, well, they look like the sexy creatures of most Hollywood films. But as it continues, the movie asks us to question our first impressions. It’s a film about not making snap judgments, in business, in love or in life.

Is there a difference when women are behind both the camera and the story? In this case, yes and no. It’s no surprise that this movie features a trio of three-dimensional women at its center. For the most part, though, its male characters are generic and cardboard-flat. There’s entitled hedge-fund guy Michael (James Purefoy), Naomi’s mentor and boyfriend, all about the money and the game. There’s the entitled tech entrepreneur Ed (Samuel Roukin), who is all about the money and the sex. The one good guy is a warm and supportive U.S. attorney who steers Samantha toward remaining in her ethical lane. Here is a movie implicitly critical of Wall Street and explicitly damning of hedge funds.

Despite the one-dimensional men, I was surprised by the film’s deceptions and detours. The greatest asset of “Equity” is Gunn, whose face is a Kabuki mask and whose skin is impenetrable as that of a female shark. While watching her I thought once or twice that hers was a one-note performance. But by movie’s end, I realized it was a symphony of invincibility and vulnerability.

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