[stana (OP)]

Whats this thing about. When scuba divers come up from the water to fast they get too much oxygen in the blood, and they can die? How does that work?

Thanks

[another_someone]

There are two problems with deep sea diving - too much nitrogen in the blood (for which divers then use helium in place of nitrogen in deeper dives), and the formation gas bubbles when coming up too fast from the deep.

The problem with gas bubbles is not that too much gas is in the blood, but that as you go deeper, and the pressure increases, so more gas dissolves in your blood.  Having more gas in your blood is not of itself the main problem (although, with nitrogen, and some other gasses, they may present certain other problems - but those problems are not the ones associated with coming up out of the dive).  The problem when coming up from a dive is that the pressure is reduced (the same problem could happen if you climb to a high altitude rapidly) is that the amount of gas that is dissolved in the blood reduces.  If this happens slowly enough, then you can breath out the excess gas (hence why you have to come up from a dive slowly).  If it happens too fast for you to breath out then the gas will form bubbles in the blood stream.  These gas bubbles, may cause no harm at all, but if a gas bubble gets stuck in a small blood vessel, it can have the same effect as a blood clot, stopping your blood flowing through the vessel, and probably damaging local tissue.  Depending where this gas bubble lodges, it may just cause a little pain in your small finger, or it could stop your heart from functioning, or it could cause damage in your brain.