The term water retention (also known as fluid retention) or hydrops, hydropsy signifies an abnormal accumulation of clear, watery fluid in the tissues or cavities of the body. Water is found both inside and outside the body’s cells. It forms part of the blood, helping to carry the blood cells around the body and keeping oxygen and important nutrients in solution so that they can be taken up by tissues such as glands, bone and muscle. Even the organs and muscles are mostly water.