In a mixing bowl, whisk together flour and eggs. Gradually add in milk and water, stirring to combine. Add the salt and butter; beat until smooth.
Heat a lightly oiled skillet over medium-high heat. Pour the batter onto the skillet, using approximately ¼ cup for each crepe. Tilt the pan with a circular motion so that the batter coats the surface evenly.
Cook the crepe for about 2 minutes, until the bottom is light brown. Loosen with a spatula, turn and cook the other side. Serve hot.
In a skillet, melt the butter and sugar over medium heat. Add the orange juice and zest, and cook until the mixture is slightly thickened.
Add the Grand Marnier and carefully ignite with a long match. Let the flames subside. Add the crepes to the skillet and coat with the sauce. Serve immediately.