I'm replaying the game and can't find it anywhere.
Used to be able to find it in White Orchard in a treasure chest. I went everywhere. Nothing.
There used to be a water hag in WO swamp that dropped it - Not there anymore.
Used to drop from drowners - Doesn't drop anymore. I killed dozens. I thought it dropped from Drowned Dead but looks like I misremembered cause W3 seems to not feature this enemy.
There was a water hag in the elven ruins you visit with Keira - also not there, just drowners.
Where the hell do I find it now ?
I know I can buy it but it's like the most expensive ingredient out there and I'm a cheapskate/hoarder.
Was ALL this drops/loot removed in some patches ? I can see the game has changed a lot but come on, I'm 10h or so into the new playthrough and I haven't found a single Water Essence. And I look everywhere, belive me.
P.S. Unless you know where to find it in the CURRENT PATCH, don't bother. I already searched all the places that I people pointed out in different forum posts around the Internet but they all talk about older versions.
EDIT: Whoops. I just realized I didn't have HoS activated so I don't know how that affects the game in general.

It's not a guaranteed drop, like many other ingredients. I have tons of the stuff, and I've never bought a single instance.

I know that used to be a rare drop from drowners but I swear I killed so many of them already I lost faith that it's possible anymore. Also 2 separate Witcher 3 wiki's don't have Water Essence listed as a drop from them.
P.S. I know it drops from Sirens later and I'll be drowning in it but I kind of need it now :)

Hmm. I have 4 dozens of this stuff w/o ever paying attention from where it comes. And it may well be that I inherited it from earlier versions (my Geralt started as 1.08 or even 1,06, unsure of it). I promise I will look out for .. what is it? Water essence? I happen to be chronically short of Mandrake Cordial. ;^D
( Drowned Dead, this sort of high-level drowner? I've seen them in W3, too. )

Yeah, it was like a 'better' drowner in previous games. And I had a memory where I found one in W3 and he dropped the 1 Water Essence I needed, but I might have misremembered that. I heard you can find them on Skellige but I'm sure I was looking for it in Velen last time. Apparently they have same drops as the drowners so that doesn't add up too.

I think the mandrake cordial (roots ?) are very rare on purpose and always have been. The thing is I had a cat potion at this moment of my last playthrough and I explored LESS that time. I even saw a LP lately where the guy found like 2 in WO and I checked the same chest and it wasn't there.
EDIT: Whoops. I just realized I didn't have HoS activated so I don't know how that affects the game in general.

Yay! The water hag in the Elven ruins that G. visits with Keira Metz dropped one. That's the only positive thing I have to say about the hag (the water hag, I mean). :)

LATE EDIT: Alright, Big Data analysis shows that 50% of water hags drop water essence. (Ahem. Two out of four had one.) ^^