A surfboard's wax holds sand from the beach that can rub against a surfer while paddling out to the break, or legs while sitting atop one's board.
A rash guard helps to prevent irritation caused by rapid impact with surface water and waves as well.
A rash guard by itself is used for light coverage in warm weather for many other watersports including surfing, canoe polo, scuba diving, snorkeling, freediving, wakeboarding, bodysurfing, bodyboarding, windsurfing, kitesurfing, kayaking, stand up paddle surfing, or swimming.
The use of nylon and spandex create a garment that is lightweight, quick drying, flexible, durable, naturally antibacterial and water wicking.
Many children, and parents, find it is much easier to put on a swim shirt as it is loose and easily slipped on.
Many practitioners wear rash guards underneath a gi or as a stand-alone garment for training in various grappling sports and mixed martial arts (MMA).
In competition, BJJ athletes are allowed to wear rash guards with long or short sleeves.