Accessing Crete requires players to be sea battle level 15 and class level 15. Once these requirements are met, it's a matter of navigating to the Straight and preparing for three waves of pirate forces. The baddies include Gibraltar pirate flagships and North Sea pirate flagships, both of which will challenge high-level players as well as lower-level types who want to advance quickly by doing the daily quest and defeating the three bosses.
There's a fair bit of incentive to run the instance due to its loot drops as well, and enterprising captains have a chance to snag buckshot cannon and dartling cannon drops, not to mention rare gold and high-grade forging materials.
[Source: IGG press release]