how do you feel real thirst?

Good evening!
How would you describe real thirst?
When I did 36 hrs dry, I was thirsty out of my mind 20 hrs into it, like in cannot-think-about-anything-else-other-than-water thirsty ...
I usually drink about 2.5 liters on a normal day, beside the raw food and its own water.
PS
3 days is quite an achievement in my opinion. what is the longest you did? you better increase gradually.