it is not only a matter of water retention, it is also a matter of metabolism and activity level. your body works in a slow down mode during moon time, and generally you feel more tired and less prone to jump around. I've noticed my best and highest weight loss is the 2 weeks after ovulation, it is also when I feel the most active, and get many things done. Then I need to slow down as moontime comes.
its definitely true. my cdc warned me of it when i had my wi during totm. but i luckily lost 5lbs! so that just shows everyone is different. x dont worry about it too much. most people retain alot of water... i usually do too