>>7213541It does add water weight, but it also increases strength and power output which increases muscle mass.
Studies have shown that you retain all the mass gains after you stop but lose the water weight (1kg roughly).
It does not cause damage to the kidneys, it's been proven in many studies.
Creatine now is the most used supplement by olympic level athletes, after multi-vitamins.
Search google scholar for creatine for studies that have been done.