On every boat there is a table with a lid on it that's used for navigation. When you take the lid off, there is a big map, a sextant, and some little boat miniatures. All the navigation tools.
You watch the navigation equipment roll away and then you feel a slap on the back of your head. Ouch! You turn around and there stands こういち, who you took with you as the navigator of this expedition. And, you just lost all his stuff!