Yes, you need to take in more water as DE can act like a diuretic.
I use a tablespoon of DE in simple water, not juice... Just pure liquid to get it down.
The next day I felt only mildly different, not negatively.
But looking in the mirror I said ok, no makeup today. My eyes were stunningly 'nice', I usually put a touch of liner, and usually darken my brows. Small touches. So I left it at just using moisturizer, and went out. A woman and I were chatting and eventually she said "you're so beautiful'. I tell you this because I had not heard this in decades, and it was day 1, following use of DE. The down side for me is that on the 2nd, 3rd day I am a bit constipated....