I'm making spinach manicotti tonight....?

This recipe looks great to me as well. Some of my suggestions would be to NOT cook the shells first as they will make them harder to hold/handle when stuffing them and a soggy noodle upon the finished cooking time of the dish. I would put your mixture in a pastry bag or zip lock bag with one of the bottom corners cut off so you can easily squeeze your mixture into the shell. Yes, the water does sound odd but is a necessary ingredient in your sauce as it will help to cook your raw noodles, it's a must have, especially with a jarred sauce which tends to be thicker than home made. I would not cover this dish as the noodles will get soggy with that lengthy cooking time (a tightly covered dish will create a lot of steam inside) the open cooking method will cook the sauce and allow the added water to cook the noodles together, while slowly melting the cheese mixture inside your noodles as well as the cheese on the top. I hope some of these suggestions help you to enjoy this wonderful recipe today, best of luck to you!