Which gas is NOT commonly found in water?

Nitrogen is not commonly found dissolved in water when compared to the other gases listed. While nitrogen is a major component of the atmosphere and can be present in water under specific conditions, its amounts are typically much lower than gases like carbon dioxide and hydrogen sulfide, which are more frequently found due to biological processes and geological factors.

Carbon dioxide can dissolve in water as a result of atmospheric exchange and contributes to the acidity of the water. Hydrogen sulfide is often found in groundwater and certain aquatic environments, especially those with decaying organic matter or reducing conditions. Methane can also be present in water, particularly in areas influenced by organic material decomposition or certain geologic formations.

Therefore, nitrogen is less commonly associated with water in significant concentrations in comparison to the other gases mentioned in the question, making it the correct choice.