Exercising will speed up the rate you get clean. 100% fact. To what degree i can not tell you. but for Certain it will help increase metabolism. No where in my post did i say it will instantly clean your system or anything crazy like that, but if you exercise regularly, than Not only will your resting metabolism increase but during your exercise you can burn about 100 calories per mile ran. now if you eat low fat during this time then you will clean even faster. your body will be burning your fat away into the blood to be filtered by the kidneys. The half life of THC is anywhere from .8 to like 10 days or so depending on your metabolism rate and body fat percentage.

There is no possible way that Aerobic exercise does not increase metabolism. I am not saying this is an instant thing. It still takes time to get clean, but it does help.

Drinking water on the other hand wont really do anything for helping you get the THC metabolites out of your fat because it is released at a constant rate according to your metabolism, but i would help you get whatever thc metabolites that are in your kidneys out. also drinking water is good for you so go for it especially if you are going to start exercising. Plus getting into shape and exercising is great for your body and will release endorphines and make you feel good and will help you keep your mind off smoking weed.