Preheat oven to 375 degrees. In a bowl blend together the flour, cornmeal, coarse salt, and fresh rosemary. Add the egg whites and the water. Stir to combine. Add more water if necessary to form a stiff dough.
On a lightly floured surface roll out the dough. Transfer it to a baking sheet. Wrap the whole red snapper completely in the dough. Press the edges of the dough to seal. Put in oven and bake for 25 minutes.
Remove the crust. Fillet and serve the fish. Lacryma Christi del Vesuvio, Mastroberardino, 1994