Ask, bluff and fish the ocean to collect four of a kind before your sharp-memoried rivals do.
Pick an opponent and ask for a rank you already hold. If they have it, they hand it over and you ask again; if not, you go fish and draw from the stock. Collect all four cards of a rank to lay down a book.
Go Fish is one of those games that seems to have always existed, and the documentary record is correspondingly thin — which is normal for games learned in childhood and passed on without a rulebook.
The one thread historians pull on runs to Italy at the end of the 15th century, and a game called Andare a pescare — "to go fishing". No contemporary description of it survives, so the connection rests on the name and on the shape of the play rather than on evidence.
What is clear is what the game is for. Asking an opponent for a rank tells the whole table what you hold, so the real skill is remembering what everyone else asked for. It is a memory game wearing the costume of a card game, which is why it works so well with children and so poorly with adults who are paying attention.
Go Fish is an original free browser version of the classic set-collecting card game, with computer opponents that remember the cards you ask for. No download needed.