The Nitrox specialty allows you to dive with a different air mixture than the standard one, that is to say, you will not find 21% oxygen, but there will be more.
The importance of being a Nitrox Diver is that it allows you more bottom time and increases your safety margin. In addition, the surface interval decreases, thus increasing the time you can spend diving.
From this specialty you will be able to increase the oxygen in your air mix up to 32% or up to 40%, depending on whether you want to do Nitrox Level 1 or Nitrox Level 2.
The specialty consists of a theory class and a dive for a price of 135€ per person.