1In small microwavable bowl, place rhubarb, water and lime juice. Cover with sheet of plastic wrap. Microwave on High 5 minutes.
2With slotted spoon, remove rhubarb from bowl. Pour remaining juices into blender. Add watermelon, strawberries and agave nectar to blender. Cover; blend on high speed until pureed.
3Divide mixture evenly into 4 individual dessert bowls. Top each with 1 tablespoon yogurt. Serve immediately.