Wash cucumbers, and cut in half lengthwise. Remove pulp, leaving a 1/4-inch shell. Chop pulp, and set aside.
Cook bacon in a large skillet until crisp; drain well, reserving 2 tablespoons bacon drippings in skillet. Crumble bacon, and set aside.
Sauté onion and reserved cucumber pulp in bacon drippings until tender. Add tomato, breadcrumbs, salt, and pepper.
Place cucumber shells in a 13- x 9- x 2-inch baking dish. Spoon mixture into shells; top with bacon. Pour water around cucumbers. Bake at 350° for 45 minutes or until cucumbers are tender.