The document discusses the relationship between water and excretion. It defines excretion as the process by which the body removes waste through organs like the kidneys, skin, liver, urethra and bladder. These organs rely on water to carry out their excretory functions - the kidneys filter waste into urine, the skin sweats out salts and heat, and the liver converts toxins into urine. Overall, water plays a key role in the excretory process by transporting and removing waste from the body.