Baja Style Tempura Fish

Name: Baja-Style Tempura Fish
Ingredients: 1 1/2 cups water; 1/2 cup fresh lime juice; 10 cloves garlic, sliced; 2 serrano chiles, stemmed and sliced; 2 teaspoons dried Mexican oregano, ground (page 161); 1 tablespoon fine sea salt; 2 pounds young shark fillet, cut into 4 by 3/4-inch strips (see headnote); 3/4 cup plus 1 tablespoon ice water; 2 1/2 teaspoons yellow mustard (optional); 1 cup bleached all-purpose flour; Vegetable oil, for deep-frying; 10 (5 1/2-inch) soft white corn tortillas (page 13), for serving; Garnish: Baja Cabbage Slaw (page 145), lime wedges, and pickled jalapeño rings