The ability of the diver to control the psychological activity under water is quite important for the protection of his life and health. That is why one must have a good psychological preparation to ensure his or her psychological alertness. A diver's psychological alertness is determined by the status of his own cognitive abilities – the qualities of the attention, perception, thought, memory, and prediction of deeds and situations. Here are various methods to train one's psychological alertness.

Regulation of Muscular Tension
By conscious loosening of the muscles, the neuro-psychological tension decreases considerably. The muscles of the arms, the back, the legs and those of face are gradually slackened one by one. The loosening should be done 2 to 3 times for about five minutes.

Regulation of Breathing
It is necessary to decrease the frequency of breathing and increase the duration of exhaling. After inhaling, the air is held in the lungs for a few seconds and then is slowly exhaled. This exercise should be done 10 to 12 times.

Idea-Motor Training
Idea-motor exercises are used when a beginner learns how to work with set number 2. The possible actions in a situation, story or instruction are mentally “done”. The effectiveness of the idea-motor training depends on the ability of the student to concentrate, and also on the clearness and the completeness of notions – the elements of movement, succession, co-operation, etc.

Psycho-Physical Relaxation 
By means of psycho-physical relaxation, the tension before entering the water can be removed and physiological functions can be mobilized. Quick wittedness and concentration of thought are obtained by cautious guidance. The physiological mechanisms are based on the effect of speech on the muscular and other systems in the organism. The conscious regulation of the muscular tension and the effect of the paradoxical phase in the brain cortex are reduced. 

The relaxation is performed with closed eyes and relaxed body. The muscles of the limbs and the torso are slackened. Consequently, a notion of heaviness, calm breathing, rhythmic pulse, warmth of body, and coolness of the forehead are triggered. Relaxation takes 5 to 20 minutes.