In a small bowl, combine cucumber, celery, green onions, vinegar, and garlic powder; set aside.
In a small saucepan, bring tomato juice and water to boiling. In a large bowl, add tomato juice mixture to gelatin; stir about 3 minutes or until gelatin is dissolved. Chill in the refrigerator about 45 minutes or until slightly thickened (consistency of unbeaten egg whites).
Stir in vegetable mixture. Divide mixture among six 5- or 6-ounce custard cups or plastic cups or pour into a 3-cup bowl or salad mold. Cover and chill in the refrigerator for at least 4 hours or until firm. To serve, unmold salad(s) onto serving plate(s).