Is that like fasting?

I'm not sure what the water diet is but if it's fasting than you won't intake the food to produce energy to safely work out. Working out without eating is dangerous.

The water diet is drinking nothing but water it only replaces your inbetween snacks not your actual meals but you have to drink before and after you eat so you feel more full. It's a good way of losing weight I've done it before... but never let the water replace your meals