NWT. What is a TANKINI TOP? The tankini is a bathing suit combining a tank top, mostly made of spandex-and-cotton or Lycra-and-nylon, and a bikini bottom introduced in the late 1990s.[1][2][3] This type of swimwear is considered by some to provide modesty closer to a one-piece suit with the convenience of a two-piece suit, as the entire suit need not be removed in order to use a toilet. Tankinis come in a variety of styles, and nice enough to enter a restaurant or anywhere with a pair of pants