Whether to go "commando" (wearing nothing underneath) is a matter of personal preference, but many experienced divers and surfers choose this option for maximum comfort and to prevent chafing. Wetsuits are designed to fit like a second skin; adding a layer of traditional cotton underwear can cause painful rubbing and "bunching" when wet. However, for hygiene reasons—especially when using a rental suit—most people wear a thin, synthetic swimsuit, speedo, or rash guard. These materials are designed to be in water and won't hold moisture against the skin like cotton does. In 2026, specialized "base layers" made of lycra or thin neoprene have become popular, as they make it much easier to slide the wetsuit on and off while providing a modest layer for changing in public areas. Ultimately, if you own your suit and find it comfortable, going nude is perfectly acceptable, provided you have a towel-changing strategy for when you emerge from the water.