The aim of this study was to analyze some of the major acoustic‐phonetic changes that occur in French when speech is produced by divers in an air atmosphere at several depths of submersion ranging from sea level to − 50 m (0, − 5, − 10, − 20, − 30, − 40, − 50m). A significant increase in fundamental frequency was found as depth increased. Submersion level seems to have no effect on duration and amplitude. Some significant differences were found in formant amplitude and frequencies. Shifts in the relative energy of formants 2, 3, and 4 were observed on vowels at the deepest conditions. The quantification of the difference in dB between the intensity of the fundamental and the intensity of the largest harmonic in the first formant suggests that phonation varies as a function of depth. At great depths, an increase in vowel effort contributes to speech distortion. These results are mainly discussed in terms of speech production strategies in deep atmosphere.