Preheat oven to 375°F. Lightly cost a 13"x9"x2" baking dish with cooking spray and set aside
Drain spinach by placing in a colander set over the sink or in a bowl. Press with a spoon to remove as much liquid as possible. Place spinach in meduim bowl.
Add the cottage cheese and 1 cup of the mozzarella cheese to the spinach. stir to combine.
Pour half of the spaghetti sauce into prepared baking dish. Add water and stir and mix.
Spoon 1-2 tablespoons cheese mixture into each uncooked pasta shell. Arrange shells in a single layer over sauce. Pour remaining sauce over top.
Sprinkle the remaining 1/2 cup mozzarella cheese evenly over sauce.
Cover tightly with foil. Bake for 1 hour or until shells are tender. Let stand 10 minutes before serving