In a skillet cook beef and onion over medium heat until meat is no longer pink; drain. Stir in taco seasoning and water. Simmer uncovered for 5 minute Add corn and soup; mix well.
Transfer to a greased 13x9 baking dish. Arrange tater tots in a single layer over the top. Bake uncovered at 350 for 30-35 minute or until potatoes are crispy and golden brown.