In challenging conditions, at what depth does nitrogen narcosis generally begin to affect a diver?

Nitrogen narcosis, commonly referred to as "rapture of the deep," typically starts to affect divers at depths around 30 to 40 meters, which translates to approximately 100 to 130 feet. Therefore, the correct choice indicating that narcosis can begin to manifest around 79 feet is accurate, as this depth can be within the range where divers might first experience its effects. The onset of nitrogen narcosis is influenced by various factors including individual susceptibility, rate of descent, and overall diving conditions, but generally, deeper depths elevate the likelihood of experiencing narcosis symptoms due to the increased partial pressure of nitrogen in the body.