The water content in a healthy adult is nearly 50 to 55%. Drinking water throughout the day in optimum volume; which is 2.5 to 3 litres, should be good enough for a healthy immune system. Warm water might improve digestion and boost metabolism. Water flushes out the harmful bacteria and toxins from our body leading to the development of strong immunity. Apart from that, the skin and other body tissues will stay hydrated and in good health. People who do more physical activity or are athletes need to consume more water. In normal males, consuming 3.7 liters of water and for women, consuming 2.7 litres of water should be good enough. We also receive water through the solid foods that we consume. Fruits and vegetables like watermelon, pineapple, grapefruit, spinach, cucumber, celery, etc. provide a good amount of water along with nutrients.