In a saucepan, cook beef over medium heat until no longer pink; drain. Stir in taco seasoning and water. Bring to a boil; reduce heat. Simmer, uncovered, for 10 minutes; set aside. Place crusts on ungreased pizza pans or baking sheets. Combine beans and salsa; spread over crusts. Top with beef mixture, chips and cheese. Bake at 350° for 13-16 minutes or until cheese is melted. Sprinkle with tomatoes and lettuce if desired.