1. Work the garlic and salt into a paste (best done in a wooden bowl or on a cutting board).
2. Combine the garlic paste, bread, vinegar, oil, cumin and 1 cup of the tomato juice in a blender until smooth.
3. In a large bowl, combine the blender mixture with the remaining tomato juice and the vegetables; chill the mixture for at least 3 hours. It can be thinned to desired consistency with ice cold water before serving.
4. Cook shrimp until just opaque in boiling, salted water, then plunge into cold water. Add shrimp to individual bowls to serve along with a generous sprinking of mint.