“Does being underwater cause high blood pressure?”

Any exercise or stress puts up your blood pressure while it is going on and for a short time afterwards. But, over time, regular exercise such as undewater swimming puts blood pressure down.

The story about blood pressure and being underwater relates to very frequent and prolonged breath-holding resulting in a drop in blood oxygen level. Over a period of years this can lead to pulmonary hypertension, especially in young women, which can be irreversible. In the past, his was a cause for early deaths in the pearl divers in the far east.