Add cream cheese, taco seasoning, 1 cup cheese and water to hamburger. Warm mixture until cheese is melted.
Meanwhile, boil jumbo pasta shells. When finished, run under cold water.
Pour jar of salsa in the bottom of a casserole dish.
Fill pasta shells with meat mixture and place in dish. Cover and cook for 30 minutes at 350. With 5 minutes left, uncover and sprinkle remaining shredded cheese over shells. Cook until cheese melts.