There goes that word "Grog" again ! I spent years in the Royal Navy drinking pusser's rum mixed 2 and 1 with water, and NEVER heard it referred to as "grog" ; "Tot" yes, even "bubbly" (hence my name) ,but I guess that , if this is an Australian song,then "grog" may well be something else, although how you would make it in sub-zero conditions beats me !