The Underwater Demolition Team the frogmen in the film belong to is UDT-4 (some members of the team wear utility jackets with artwork of a large number "4" and a shark on the back). The real UDT-4 in World War II saw combat in the invasions of Okinawa, Saipan, Guam, and the Philippines. Like the fictional Team in the film, the real UDT-4 had one of their boats hit and sunk by Japanese fire at Leyte, and left a sign on the beach at Guam to welcome the invading Marines.