1. Peel yuca, and cut into 1/2-inch cubes to measure 1 1/4 cups. Place yuca in a medium saucepan; cover with water. Bring to boil over high heat. Cover, reduce heat to medium-low, and simmer 25 minutes or until tender. Drain yuca in a colander over a bowl, reserving 1/2 cup cooking liquid. Return yuca and reserved 1/2 cup cooking liquid to pan; mash with a potato masher until smooth. Discard any tough fibers.
2. Place garlic on a cutting board; mash to a paste by dragging and pressing broad side of knife over garlic several times. Combine garlic, shrimp, lime juice, and 1/4 teaspoon salt in a medium bowl. Let stand at room temperature 30 minutes.
3. Heat a large skillet over medium-low heat. Add oil to pan; swirl to coat. Stir in annatto seeds, and cook 5 minutes or until oil turns deep orange in color, shaking pan frequently. Remove from heat; let stand 10 minutes. Discard annatto seeds, reserving oil in pan.
4. Heat pan over medium heat until annatto oil is hot. Add onion and bell pepper; cook 6 minutes or until tender. Add tomato; cook 10 minutes or until tomato breaks down, stirring occasionally. Mash mixture with a wooden spoon. Add shrimp with marinade, coconut milk, and Scotch bonnet. Reduce heat to low, and simmer 3 minutes, stirring occasionally. Stir in reserved mashed yuca, remaining 1/4 teaspoon salt, and 1 tablespoon cilantro; cook 2 minutes or until shrimp are done. Spoon shrimp mixture into shallow bowls; sprinkle evenly with remaining 1 tablespoon cilantro, and serve with lime wedges.