Both cooked and raw shrimp work. As I see it there are advantages to cooking them. The first is color. Cooking shrimp turns them orange and white, which is more visible than when in its raw state. Another is toughness. Has anyone ever eaten shrimp that has been overcooked? It becomes tough and stringey. Cooked shrimp tails used in conjunction with a large-profile drift bobber probably slams them in high-water.