How the ‘Waves’ cast bonded over road trips, YouTube videos and long talks

The afternoon before receiving a rapturous ovation at the Toronto International Film Festival premiere of their film, the young cast of festival breakout “Waves” looked back at the intense bonding experience of making the movie.

Alexa Demie described the “getting to know you” crash course she and Kelvin Harrison Jr. shared in order to develop the passionate but troubled chemistry between their characters, whose disintegrating relationship helps propel the film’s first half.

After mesmerizing Sundance audiences earlier this year in the drama-thriller “Luce,” Harrison enthralls in “Waves” as Tyler, a star athlete struggling to measure up to the driven image of perfection his father (Sterling K. Brown) has molded him in.

Those pressures spill over into his relationship with Alexis (Demie), a young woman who’s also figuring out the person she wants to become.

The two actors had just a week to get to know each other and get inside the toxic dynamic that spirals from their characters.

“We watched a lot of YouTube videos on codependent relationships and toxic relationships,” said Demie, who stars as Maddy on the acclaimed drama “Euphoria.”

“Shout out to Lisa A. Romano,” added Harrison, who explained that the life coach’s online seminars helped the actors understand their onscreen dynamic.

Russell, meanwhile, plays Tyler’s sister Emily — a shy introvert who comes out of her shell as she gets to know a classmate, Luke (Lucas Hedges).

Hedges and Russell recalled the three-day road trip they took with director Trey Edward Shults and director of photography Drew Daniels to capture intimate, documentary-style scenes for the film. “I don’t even know where we were,” she laughed. “The bus broke down! We were running one day and we waved at the bus and the next thing we knew, the tire flew off.”

“Waves” will be released by A24 on Nov. 1.