Two men answer the call of the ocean in this romantic fantasy-adventure. Jacques and Enzo are a pair of friends who have been close since childhood, and who share a passion for the dangerous sport of free diving. Professional diver Jacques opted to follow in the footsteps of his father, who died at sea when Jacques was a boy; to the bewilderment of scientists, Jacques harbors a remarkable ability to adjust his heart rate and breathing pattern in the water, so that his vital signs more closely resemble that of dolphins than men (he even considers a school of dolphins as his extended family). As Enzo persuades a reluctant Jacques to compete against him in a free diving contest — determining who can dive deeper and longer without scuba gear — Jacques meets Johana, a beautiful insurance investigator from America, and he finds that he must choose between his love for her and his love of the sea.

Fred, a raffish safe blower, takes refuge in the Paris Metro after being chased by the henchmen of a shady businessman from whom he has just stolen some documents. While hiding out in the back rooms and conduits of the Metro, Fred encounters a subterranean society of eccentric characters and petty criminals. Despite being pursued by the henchmen, Fred finds the time to flirt with Héléna, blow a safe, rob a train, evade the hapless Metro police, and start a rock band