A plunge neckline swimsuit that actually works uses structured support to keep the neckline in place and secure. Without the proper construction a plunge is just anxiety waiting to happen. Good plunge construction uses underwire or a hidden support panel or both. The neckline needs to be angled in a way that works with your body shape and not against it. A sharply angled plunge reads different than a more gentle one. The plunge also needs to not create spilling or gapping depending on how your chest is proportioned. These are the swimsuits where the plunge is intentional and engineered not just low-cut and hoping for the best.