Dividing the Plunder is an activity only available at Ports. In this mode, if they decide to divide the plunder, they can choose whether to:
Advance to Journeyman from Apprentice
Advance to Adventurer from Journeyman
Advance to Rogue from Adventurer
Finally advance to Swashbuckler from Rogue
Dividing the Plunder is required at some point in the game, regardless of the player's success. Mass amounts of plunder will temporarily appease the crew, but eventually they will demand to set in port and divide the plunder. This is marked by the crew happiness bar - when the crew becomes unhappy, despite the player's vast wealth, they may even commandeer a ship from the fleet and sail it into port.