Place water, milk, flour, eggs and salt into blender (in that order makes it easier to scrape the unmixed flour off the sides) and blend at lowest setting.
After 30 seconds pour in melted butter and continue to blend at lowest setting for two minutes (make sure to stop the blender after about 15 seconds and scrape any unmixed flour off the sides).
Warm a non-stick crepe pan (8" or 10" pans are the best size) over medium heat.
Starting with the crepe pan already tilted, pour in 1/4 cup to 1/3 cup of batter (depending on pan size) and quickly tilt the pan spreading the batter to the edges (this should make for a nice thin crepe).
Once the edges start to curl up slightly, inspect the under-side to see if it's a light golden-brown.
This step is up to you, but some people like to flip the crepe for about 10-15 seconds just to give it a more "finished off" look.
Fill with fruit or Nutella or cinnamon-sugar, or my favorite, ham & Gruyère (don't forget to add pepper!).