Thanks for this, reading "water fast" and "3 days" gave me a shot of adrenaline. The "water" prefix is just confusing, the word for abstaining from food is just "fast" for those interested.
dry fasts aren't always what they appear. if you have significant glycogen stores in your body as you begin your fast you wont be dehydrated for the first day or two as water is freed. what usually happens is someone who starts glycogen endowed discovers that they aren't thirsty when they start fasting and tout it as dry fasting.
What you thought of (not even drinking water) is called a dry fast. It is a thing, but for obvious reasons is much more intense and shorter in duration.