Grog

Grog is a term used for a variety of alcoholic beverages. During the early modern period , sailors required significant quantities of fresh water on extended voyages. Since desalinating sea water was not practical, fresh water was taken aboard in casks, but quickly developed algae and became slimy. Stagnant water was sweetened with beer or wine to make it palatable, which involved more casks and was subject to spoilage. As longer voyages became more common, the storage of the sailors' substantial daily ration of water plus beer or wine became a problem.

Source: Wikipedia