Preheat ovn to 325. In a large skillet, brown meat & drain off fat. Stir in beans, tomatoes, onion, taco seasoning, soup and water. Simmer over medium low heat until everything is well combined and heated through.
Grease a 9x13 casserole dish. Put down a layer of crushed tortilla chips, followed by a layer of the cheddar cheese. Repeat layers. Cover with foil and bake for 20-30 minutes, or until bubbly.
Remove foil and place under the broiler just until the cheese starts to brown.