Abstract: The effects of underwater hatha yoga on physiological variables, with and without scuba diving equipment, were investigated on 20 healthy sport divers before and after the underwater yoga exercises during 6 weeks. A static apnea test on water surface was applied by facial immerging in water at 2-min intervals, using two different methods of breath-holding which are called GPB and HV, during this test we measured the heart rate and lung function using pyrometer , E.C.G , and the limit of residual air pressure in SCUBA tank after 30min dive. After this test we found an observable increase in the apnea time and residual air pressure in SCUBA tank, and this was attributable to a decrease in heart variables and an increase in lung function. Apnoeic time tended to be larger after underwater SCUBA exercises .This results may increase the efficiency in some SUCBA diver’s skills and also gives more safety and relaxation in SCUBA diving program.