Rarely has a movie’s title been so apt as that of “Waves,” a film that makes you feel like you’ve been knocked flat over by a fierce current — only to be rescued by a gentle, soothing flow of warm surf that arrives in the nick of time.

This third feature by the gifted young writer-director Trey Edward Shults, a portrait of an upper-middle class black family in Florida, rewards repeat viewing. There’s just so much to absorb, from the assault of sound and bright color and the propulsive soundtrack in the film’s first half, to the more reflective pace and subtle glow of the second. (The supremely confident Shults takes his time; the film runs two hours and 15 minutes.)

And we haven’t even gotten to the performances yet. “Waves” offers up a sextet of them, all superb. The most recognizable names are Sterling K. Brown, who plays a flawed and domineering but loving patriarch, and Lucas Hedges, deeply winning as the love interest for the family’s daughter.

But prepare to be bowled over by two relative newcomers: actress Taylor Russell, who quite simply has the most expressive young face to be seen onscreen in many a season, and Kelvin Harrison Jr., who can be cocky and vulnerable in the same split second. Both of these wonderful young actors break our hearts. We’ll surely be seeing them again and again.

Renee Elise Goldsberry and Alexa Demie round out the cast with empathetic and appealing work as, respectively, a harried stepmother struggling to hold things together, and a fun-loving, passionate girlfriend.

Shults, who is white, has said he did not initially plan for the family in “Waves” to necessarily be a black one, but wanted first and foremost to work again with Harrison Jr., and gave him the choice of roles. Harrison chose to play the son, Tyler.

The film begins with the most peaceful of images: a young girl riding on a bicycle on an empty road, sun squinting through the trees. But then we move to a different vehicle: a car ride shot in a dizzying (literally) 360-degree shot.

This first part of the film, focusing on 17-year-old Tyler, unfolds with startling speed. The camera rushes in, out, and around in circles, reflecting the frenetic pace of Tyler’s life.

That life is composed of competitive wrestling, homework, training, beach outings and late-night parties. But life with dad Ronald takes its toll. At the diner after church one morning, father challenges son to an arm wrestling match right at the table. At home, he lifts weights with his son, exhorting him to work harder.

The point is to excel. “We are not,” father tells son, “afforded the luxury of being average.” It’s hardly a shock when we see Tyler popping painkillers and swigging alcohol to stay afloat.

The balance of Tyler’s high-octane life is disrupted, dangerously, by two sudden setbacks: an athletic injury and a major complication involving his girlfriend. His sleek veneer starts to crumble; we watch as he becomes a frustrated, angry kid. He tests boundaries with his parents and provokes fights with Alexis.

And then tragedy strikes. It comes with crushing force. And the film takes a dramatic pivot.

As the family copes with the unthinkable event that’s engulfed them, suddenly Emily (Russell), the unheralded sister, becomes the focus. And the movie slows down, palpably.

One day, sitting alone, Emily is approached by Luke (Hedges), a wrestling teammate of her brother. He strikes up a sweetly awkward conversation and asks her out.

By this time we’ve become, emotionally, Emily’s surrogate parents. Is Luke a good guy or a bad guy, we wonder? So does she.

There are a few stunning scenes in this latter part of the film, which takes place in the sultry Florida summer: An emotional father-daughter fishing excursion. An idyllic swim with manatees. An unexpected trip to a hospital to close a painful chapter.

Shults can achieve a lot in a just a few seconds. A quick overhead shot in a prison cafeteria, wordless, delivers a punch to the gut.

“Waves” is about family, but even more about love — different kinds. The tempestuous love between teenagers. The more mature love between parents. Complex inter-generational love.

Love ebbs and flows in this movie. It can destroy — but also heal. If the head-spinning first half is about passion and violence, the second half is about acceptance. At a swimming hole one day, Emily, just beginning to emerge from her trauma, hesitates before jumping off the rocks.

“Take a leap of faith,” somebody calls out. It’s a throwaway line, but it seems to encapsulate the generous heart of the film. Emily jumps — creating her own little waves.

“Waves,” an A24 release, has been rated R by the Motion Picture Association of America “for language throughout, drug and alcohol use, some sexual content and brief violence — all involving teens.” Running time: 135 minutes. Three and a half stars out of four.

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MPAA definition of R: Restricted. Under 17 requires accompanying parent or adult guardian.

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