Diving response or diving reflex is the body's physiological response to the submersion in cold water. It is characterized by three major physiological responses which are the apnea, bradycardia, and peripheral vasoconstriction. This experiment was conducted in order to determine how the cold temperature of water affects the heart rate. The control group were the test subjects' breath for twenty (20) seconds while sitting, and three (3) treatments were also applied wherein the test subject’s face must submerge in water for 20 seconds in Treatment 1 at 26°C, Treatment 2 at 16°C, and Treatment 3 at 5°C. The results show that facial immersion on water was a sufficient stimulus for diving reflex to occur. The relationship between the heart rate and the temperature is directly proportional. The mean normal heart rate of subjects was 109.33 ± 11.17. At ~26°C, the heart rate decreases which became 81.00 ± 4.93 then became 71.33 ± 5.36 at ~16°C. Lastly, 64.33 ± 4.98 was the mean heart rate at ~5°C. The diving reflex exhibited in…show more content… This reflex is also defined as characteristic pattern for respiratory, vascular and cardiac responses activated by breath-hold diving (Gooden, 1994). Also it optimizes breathing to allow face immersion extended for periods of time. Diving reflex is excellently exhibited by aquatic mammals particularly dolphins, while humans in the other hand displays the weaker version of the reflex (Perini et al., 1998). This kind of reflex is characterized by the three major physiological responses which are the apnea, bradycardia and the peripheral vasoconstriction. Peripheral vasoconstriction is mainly achieved by selective vasoconstriction and bradycardia. Blood flow divert away from the organs that can perform anaerobically, but maintained in organs sensitive to being lack of oxygen or asphyxia, such as the brain and the heart (Schagatay and Holm,