 Deep dives should be made only after a gradual training to test the individual diver 's sensitivity to increasing depths , with careful supervision and logging of reactions . Diving organizations such as Global Underwater Explorers ( <unk> ) emphasize that such sessions are for the purpose of gaining experience in recognizing the onset symptoms of narcosis for an individual , which are somewhat more repeatable than for the average group of divers . Scientific evidence does not show that a diver can train to overcome any measure of narcosis at a given depth or become tolerant of it . 
