Six Player Modification
From Bert Dreifuss on BGG
The sixth player's color is black.
Take the unused Legendary Pirate's black ship miniature.
Make a color copy of the ship's mat, and laminate it.
Purchase a small wooden plug and four 25mm black gasket caps, rubber washers, or key identifiers at a local hardware store. Color or paint the wood plug in black and use it as the fame marker. Use the gasket caps/washers as strength markers.
Use a 6-sided die in place of a Navigation wheel, matching its up face to the number of the Island you intend to navigate to.
Pirates of Legends
For a more challenging set of encounters with the Legendary Pirates, try the following semi-cooperative variant. If, at the end of the game, some of the Legendary Pirates haven't been called on deck and successfully defeated, they must be collectively defeated in one last final no-holds-barred battle. If this battle is lost, then all players lose, regardless of their individual score! (Obviously, players should try and take on the Legendary Pirates individually earlier in the game rather than face the whole of them in the last round, as things will get quickly bloody then!
Two player variant
From Joe Casadonte on BGG
Each player plays 2 ships. A normal 4 player game ensues with the following exceptions:
Put the two Legendary Pirates black ships in play, as in a 3 player game
You cannot send both of your ships to the same Outer Island (though you can send them both to Treasure Island)
If one player forgets and sends both of his ships to the same island intentionally, then they must fight each other. The opposing player chooses which ship to play.
Each boat scores itself individually. What happens next is optional.
Scoring - Option #1 (Social Gaming)
Score both boats individually, then add them together. The player with the higher total wins.
Scoring - Option #2 (Serious Gaming)
Score both boats individually. The player with the highest single boat wins. This allows players to sacrifice one boat for the benefit of the other.
Scoring - Option #3 (Hard-core Gamers)
Score both boats individually. Throw away the higher score, and the player with the highest score for the remaining boat is the winner. This forces players to develop both boats somewhat evenly (with the possibility that the higher boat will sacrifice to help the lower boat catch up).