Lung over expansion injury if he holds his breath on ascent like many free divers naturally do. He was taking compressed air breaths at depth and then ascending

Lung over expansion injury if he holds his breath on ascent like many free divers naturally do. He was taking compressed air breaths at depth and then ascending. If you fill your lungs at 33ft and ascend, the gas will double in volume at the surface, causing tons of damage and bleeding.