[McDyver]

Very broadly, when scuba diving you're breathing gas at the same pressure of the depth at which you are. So the deeper you go, the greater the pressure of the gas that is being dissolved into your tissues. You don't feel this pressure, only the pressure in the body's "hollow" spaces, like sinuses, Eustachian tubes. That's why you need to equalise on the way down.

When you dive to 50m, the feeling of "being dizzy" happens when diving on air. This is due to Nitrogen narcosis. To minimise this, in technical diving, helium is added to the mix, to reduce the percentage of nitrogen and minimise the narcosis.

Going down to 332m, as you correctly say subjects you to a pressure of 34 Bar. To dive this deep you need to be breathing 4% Oxygen, maximum (compared to 21% that is in air we breathe at the surface). At this level, making the mix needs to be extremely precise and you need to be sure your instruments are properly calibrated, as a 5% mix can potentially kill you at that depth.