Kiefer Safer Swimmer TPU Large Swimming Buoy Are you tough on your swim gear? If so, the SaferSwimmer TPU Swimming buoy is for you! Made from Thermoplastic Polyurethane, the same material used in inflatable boats and whitewater rafts, the SaferSwimmer TPU Swimming Buoy features a stronger material than the classic Kiefer SaferSwimmer. Be seen, be safe, and enjoy swimming in the open water worry free with the SaferSwimmer TPU.