Long swim trunks, also known as JAMS, are a type of swimwear that extends to the knee or mid-thigh. They are designed to provide more coverage and protection than traditional swim trunks, making them ideal for swimming in cold water or for activities such as surfing or bodyboarding. JAMS are usually made from quick-drying materials such as nylon or spandex, and often feature an elastic waistband for a comfortable fit.