Bring the rice and water to a boil in a saucepan over high heat. Reduce heat to medium-low, cover, and simmer until the rice is tender, and the liquid has been absorbed, 20 to 25 minutes.
Preheat an oven to 350 degrees F (175 degrees C). Butter a 2-quart baking dish. Combine the bread and milk in a mixing bowl; set aside.
Melt the margarine in a skillet over medium heat. Stir in the garlic, onion, and bell pepper until the vegetables begin to soften, about 3 minutes. Add the shrimp, and cook until the shrimp are no longer translucent, about 3 minutes more. Stir the shrimp and rice into the soaked bread along with the cream of mushroom soup, parsley, and lemon juice. Pour this mixture into the prepared baking dish. Sprinkle with paprika.
Bake in the preheated oven until the top is golden brown, and the casserole is hot and bubbly, about 30 minutes.