Called Les Marches, the outdoor furniture will be arranged on top of the rockery of the private C Beach for Quinzaine des Réalisateurs – the Director's Fortnight – an event held alongside the film festival later this month.
The modules, which look like slightly squashed rectangles, were designed by Smarin in collaboration with French artist Céleste Boursier-Mougenot to provide a temporary place for people to rest, meet and party during events.
"We created a modular system to build easily arenas, amphitheatres, or soft seating 'floating' areas," Smarin founder Stéphanie Marin told Dezeen.
"The 85 Marches create a very aesthetically radical space nearly the sea," she explained. "These multiples can be moved around so easily that it fits perfectly to the Quinzaine experimental spirit."
Like the pebble-shaped blocks that Smarin previously created for their Nap Bar in Dubai, the seats are made from foam so that they are lightweight enough to move easily on site and soft enough to clamber up.
The temporary installation can also be easily transported and reassembled in different locations, and angled sides make it easy to change the layout.
For instance, the blocks can be stacked around a circle to create stepped seating like a theatre, they can be arranged on one level to form a cushioned platform, or can be scattered in a more chaotic way to allow for more casual activities.
"Their arrangement is free, allowing both to deconstruct the decor or, contrary, to define flexible arenas, squares or staircases soft to the touch," said Marin.
A non-toxic grey paint forms a protective layer across the exterior and gives it a creased leather-like look.
"They look like common concrete building blocks," added the designer. "To me, they just are abstract simple shapes. I love their open efficiency."
The Quinzaine des Réalisateurs runs from 11 to 22 May 2016, in tandem with the main festival, and will showcase a mix of fiction features, short films and documentaries.
It won't be the first time Les Marches has been shown – the seating was previously installed in the French Pavilion during last year's Venice Biennale and at the Palais de Tokyo in Paris.
Other recent examples of foam seating installations include full-size replicas of playground designs from architecture's Brutalist era, created by Assemble in London, and a foam display and seating system to present information to children in museums.