Men: suit may not extend above the naval or below the knees. Women: suit may not cover the neck, go past the shoulder, or extend below the knee. Only FINA-approved suits may be worn in USA Swimming competitions. Swimsuits must be non-transparent and appropriate.

Suitcase rules vary significantly by location, but the general "standard" for public pools and water parks in 2026 focuses on safety, hygiene, and "modesty" codes. Most commercial water parks (like Disney's Typhoon Lagoon or Universal's Volcano Bay) strictly prohibit swimsuits with exposed metal zippers, buckles, or rivets, as these can damage the fiberglass surfaces of the slides and potentially injure other riders. Regarding style, "thong" or "G-string" style bottoms are often banned in family-oriented resorts in the U.S. and UK, where "full coverage" or "appropriate family attire" is mandated. In contrast, many European beaches are much more permissive regarding nudity or minimal coverage. For hygiene, almost all public pools require that "swimwear" be made of specific materials like nylon or spandex; wearing "street clothes" like cotton T-shirts or denim shorts in the water is usually prohibited because cotton fibers can clog the pool's filtration systems and harbor bacteria. Additionally, for infants and toddlers who are not yet toilet-trained, "swim diapers" (both a disposable layer and a reusable plastic cover) are a non-negotiable legal requirement in almost all public swimming facilities globally.