All the sound in the film - the wind, the trees and the water - was naturally recorded on location.
Alain Guiraudie said he tried to write a heterosexual version of this story in the scripting stages but it did not work. He said, this story needed to be a story about men and the two leads needed to be equal to each other in every way. That is why he made it a love story between two men.
Director Alain Guiraudie based the setting of the film - the lake of the title - on a real lakeside cruising ground he knew, but he did not film at that exact location and chose a different location that was warmer and sunnier. He specifically picked a beach next to a lake as opposed to one next to a sea because with the sea, the horizon is too far and too wide and he wanted to constrain the setting.
There is not a single interior shot in the entire film. It was filmed completely outdoors and the entire story takes place outdoors. There is only one location in the movie - the lake (of the title) and its surroundings. Director Alain Guiraudie wanted to maintain the unity of space, time and action as in classical theater so he based the entire film in a single location, as if in a play.
There were no hair-dressers or make-up artists on the film's crew and none were employed for the film.