Combine 1/2 cup tomato, shrimp, 1 tablespoon each of cilantro and lime juice, 1 teaspoon jalapeño, and 1/4 teaspoon salt in a medium bowl. Cover and chill 30 minutes.
Meanwhile, combine avocado, water, 2 tablespoons cilantro, and remaining lime juice and jalapeño in a blender; process until smooth. Add sour cream and remaining 1/2 teaspoon salt; process until well blended.
Pour soup into a large bowl; stir in remaining 1/2 cup tomato. Cover and chill 30 minutes. Ladle soup evenly into 4 bowls; spoon 1/4 cup salsa into center of each serving. Sprinkle each serving evenly with remaining cilantro.