Olivier Ducastel & Jacques Martineau - Crustacés & coquillages AKA Cockles & Mussels (2005)

Quote:
For summer vacation, Marc and Béatrix take their two kids to the seaside house of Marc’s youth, where their daughter takes up with a biker and their sons roams the beach with his best friend, who is in love with him. Things get steamier when Béatrix’s lover Mathieu shows up, and Marc’s old flame appears.