Sometimes it can get hella boring. Nothing fun happen, you're just grinding skulls and treasures.
But sometimes it can be magnificient, you'll find yourself in the middle of a storm while an aggressive crew is trying to sink your ship to get your loot, while your dog is howling to the death because a lighting just hit and your ship is burning. And when those moments happen, it might as well just be one of the most memorable multiplayer moments you've ever had.