There are two key differences between Regular and UV Protective Swimwear: Fabric Type and Style Design;
Regular and sun protection swimwear both use stretch fabric that is suitable for use in water, mostly made from Nylon, Lycra, Elastane, Spandex or Polyester yarn. The quality and performance is linked to the fabric composition example Nylon/Lycra or Polyester/PBT and to the weight example 170gsm or 200gsm (grams per square meter), however to achieve UV protection status the fabric need to be tightly knitted in order to block the sun UV rays from getting through and reaching the skin, hence some regular swimwear fabrics which are not tightly knitted are not suitable for sun protection. The highest UV protection ratings a fabric can achieve is UPF50+ which blocks over 97.5% of the sun UV radiation, even though some swimwear and clothing fabrics can achieve 100% UV block, however under the UPF ratings system the maximum protection statement allowed is "Over 97.5%" and not "100%", this is due to the fact that the UV protection a fabric can achieve may be lessened when wet or over stretched according to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Some uses the term SPF to refer to swimwear and clothing UV protection, this is incorrect, SPF refers to Sunscreen Protection Factor and is specifically used to measure the UV protection provided by Sunscreen.
The design difference is easily visible between traditional swimwear styles which tends to follow fashionable trends and personal tastes where more skin is exposed, and the sun protection swimwear styles which takes into consideration the need to cover as much skin as possible and minimize exposure to the sun UV radiation; Sun protective full body coverup swimwear designs such as stinger suits, dive skins and full body swimsuits covering the arms and legs have the ability to keep the skin protected all day long from the harsh UV rays which can cause sunburns, skin damage and worst case scenario skin cancer.