A game of exploration and colonization of the new world. At the start, each player decides what country they will be from and takes the appropriate counters. The board represents a map of the Atlantic ocean with Europe in the NE and the North America to the WSW.
The object of the game is to sail to the New World and load up your ships with wealth from your colonies to bring back to Europe. The other players are trying to do the same but they can try to intercept your ships and either sink them or take your cargo.
There were two main editions of the game. The first accommodated 2-6 players and came in a brown box (there were apparently actually two versions in a brown box, but the differences between them are apparently very minor). The second is in a blue box, takes only 2-4 players (there are also solo rules, but the gameplay is very different with them), and has some changes from the earlier edition. There was an expansion kit for this edition which added the other two players, but which appears not to have been widely distributed.
There was also a "Spanish Main Up-Date Kit" to upgrade the 1st to 2nd edition.