How diver can be Angina effect?
We find one fact in science that gas can be dissolved in liquid and if pressure increased then gases will more soluble. Easy illustration is a soda water bottle. When open the lid, the carbon dioxide will out of bottle and will be bubbles in soda water and float away from the bottle. It because in a soda bottle will have pressure higher than atmospheric. When we open the lid, then the pressure is reduced. It unable dissolved gases into the solution, gases need to escape from the solution by emerged as bubble then escape into the atmosphere.
In the same event may occur in the human body, if humans live in a high pressure environment and dissolved gases in the blood than normal. The gas dissolved in the blood than normal, this is not harmful in any way. If the pressure rapidly drops then gas will bubble up in the blood, and bubbles of gas may be large enough to be able to block the flow of blood. These symptoms usually occur in the chest area and this symptoms is called Angina effect. So people diving in the deep sea then very quickly appeared to the surface, they often cause Angina effect.