"Every sailor, every Admiral knows that you're not allowed to shoot survivors of a shipwreck. It's absolutely clear from the very first... there was a case in 1918, (HMHS) Llandovery Castle, full of Canadian nurses which was sunk by a German U-boat and they then surfaced and machine-gunned the survivors, the nurses and the sailors who had survived the sinking. And even a German court condemned them for that war crime."
Geoffrey Robertson
https://www.abc.net.au/listen/programs/latenightlive/geoffrey-robertson-war-crimes-/106097984