2 what happens if a diver comes to the surface too quickly?

Answer 1

it depends on the depth you are assenting from and the speed.

However if your were on 30m deep and assented too fast without equalizing and continuance breathing you can hurt your lung and ears

Answer 2

Please see the answer in the question "What does decompression mean in diving?"

Answer 3

Nitrogen that is dissolved in the blood stream turns back to gas and forms bubbles in your blood stream and throughout your body. Usually fatal.