Heat tomato soup and cream cheese in double boiler. Gently stir the mixture with a wire whisk to blend. In a small bowl, dissolve gelatin with the water. When hot mixture is completely blended, add dissolved gelatin and stir to blend. Cool mixture at room temperature. Make sure it's completely cool. When cool, add shrimp, onion, celery, mayonnaise, lemon juice and salt. Blend mixture thoroughly. Pour into 5 cup mold and chill for 4 hours. Unmold to serve and decorate with parsley sprigs and lemon wedges.