Not nice, that’s for sure! Although it’s the oxygen in the air we need to live, air is mostly nitrogen. Normally nitrogen dissolves in our blood. When scuba divers come back to the water’s surface too fast, dissolved nitrogen can form bubbles. These bubbles block blood vessels, causing decompression sickness.
One symptom, painful muscle spasms, is known as ‘the bends’. The blocked blood vessels also make it hard to breathe, which is known as ‘the chokes’.