In a large nonstick pan, add ground beef and onions. Cook until beef has browned, about 3-5 minutes, making sure to crumble the beef as it cooks; Pour into a colander, in the sink, and drain excess fat. Add beef back to pan. Stir in taco seasoning, corn, and water. Mix well. Bring to a boil, turn heat down to simmer, and cook uncovered. Stir often, for 5 minutes.