I've done something similar on a number of occasions.
Instead of just water, however, I'll usually make sure to have a nice batch of broth cooked up.
I'll drink cold water and warm broth through the day, and, if I start to get a real severe gnawing hunger, I'll pop a spoonful of coconut oil mixed with a little coconut butter (and maybe a little cinnamon and sea salt). The coconut oil/butter mix always kicks the hunger down several notches and I'm fine to go back to water/broth for the rest of the day.
If I start the fast the night before (dinner around 8-9pm), fast overnight, wake up around 9am, go through the day with light activity (chores around the house, walking, riding my bike), back to bed at 10-11pm, and then awake again at 9am, that puts me right at 36hrs. At this point, I'll usually have something "easy" to digest, like a few eggs cooked in animal fat or a fruit & veg smoothie with some protein powder. At this point, I'll just roll right back into my regular food and activity routine.