What does the nickname beaters mean in Royal Navy or Royal Marines physical training?
Short answerClub swingers is the naval term; beaters may be older Royal Marines wording connected with beating up for the Commando Course.
NotesThis exchange corrects the earlier nickname used for physical-training instructors. Club swingers is identified as the Royal Navy term. Beaters is less certain and may instead come from older Royal Marines usage. The possible link is beating up, the intensive self-preparation undertaken before attempting the Commando Course.