Corset Mermaid Dresses & Windsor Open Back Halter V Neck Corset Ruched Mermaid Maxi Dress With Slit Dresses Luxe Knot Shoulder Open Back Mermaid Hem Maxi Dress Poshmark Dresses Luxe Knot Shoulder Open Back Mermaid Hem Maxi Dress Poshmark. Make a bold statement in this trumpet mermaid prom dress. Featuring a halter neck connected to a plunging V neckline and an open back, this dress offers a daring and elegant look. The corset style bodice provides a sculpted fit, while the fitted mermaid silhouette and high slit add drama and sophistication.