Our Lula, Mira, Serena and Taali swim dresses have a built in bodysuit and removable bra cups. These swim dresses are one-piece styles and can be worn with or without swim bottoms. You do not need to wear anything underneath these styles. Our Diana and Maya swim dresses are open swim dress styles and do not have a built in bodysuit or removable padding/chest support. Both swim dresses are made to attach to any of our swim bottoms with an adjustable secure button tab (to prevent floating/riding up in the water). For comfort and support, we would also recommend the Lanuuk bikini, specifically designed to be worn underneath the Diana and Maya swim dresses as the bikini bottoms can attach to the swim dress with the secure button tab.