The easy answer is because I spend too much time working out in the pool (2hours every day) this is under the instruction of my doctor, so I do it. I'm not a stranger to an intense workout regimen, as I have been consistently working out in the gym for 11 years (4-5 days a week 2 hours a day) now post injury (c5-c7, walking quad). Its just recently that I have incorporated the pool into my routine. It seems even if I spend less time than the 2 hours I'm still completely beat. Is it something to do with the way the water affects the body, since I can do more in the water the body doesn't really feel the fatigue until after? tia