@jonny A presentation of decompression injury: air gets trapped in the lungs during ascent/surfacing, and escapes into the thoracic cavity. It goes up the trachea and exerts pressure on the vocal chords. Caused either by holding breath during ascent (extremely dangerous in SCUBA diving), or due to some preexisting problem with the lungs. I was present a long time ago when an ex-smoker had the injury with "Donald Duck symptom" (luckily, he didn't have embolism).