Almost every swimsuit contains spandex, which can stretch out and break down if exposed to perspiration and body oils. Therefore, removing those contaminants as soon as possible is important to help a swimsuit keep its shape. The chlorine in pools and hot tubs can harm a swimsuit's elasticity, too, and cause the fabric to change color. White swimsuits are particularly susceptible to chlorine and will turn yellow as it strips away the white fibers surrounding the inner yellow core of synthetic fibers. Thus, it is important to thoroughly rinse your swimsuit in clear water after every use.
But deep cleaning doesn't need to be part of your routine after each use. Several manufacturers, including REI, Patagonia, and Fair Harbor, recommend rinsing after every use, then deep cleaning after every three to five uses.
Washing a bathing suit is easy, but it should be done by hand. If you absolutely must wash a bathing suit in the washing machine whether it's by itself or with other clothes, put it in a mesh bag meant for delicate garments, use an ultra-mild detergent, and choose the delicate cycle.