In modern swimwear, a bandeau is a strapless garment worn around a woman's breasts. It may be fastened in the front or back or be sufficiently elastic so as not to need a fastener at all. A bandeau may come with a detachable halter strap, for extra support.
The strapless nature of the bandeau bathing suit means that you can tan your upper body without developing tan lines on your shoulders. Perfect to show off your beautifully tanned shoulders.