Floating Flower Tip - Most flowers float pretty well on their own until they start to pool with water and slowly sink. For a longer lasting centerpiece, use bubble wrap to make little skirts for your flowers.
The hardy, low maintenance climber star jasmine (Trachelospermum jasminoides) is well behaved. It has glossy dark green leaves and, from midspring to late summer, is covered in deliciously scented white flowers. its also tolerant of light to medium frost.