The term SEA SPIRITS can be broken down into two crossword solutions: GROG (4 letters). GROG is an alcoholic beverage made from rum, water, and sometimes lime juice. It was originally created by British sailors in the 18th century as a way to make their daily ration of rum more palatable. The name 'GROG' is derived from the nickname of British Admiral Edward Vernon, who was known as 'Old GROG' due to the grogram cloak he wore.