You'll need to roll survival if you want to find that boat, I'd say DC14 since the thing is moving in a straight line after all, but on the other hand swamp isn't the easiest thing to navigate. It'll be quite difficult to get there by foot too, and you may run into local fauna. Just a reminder that there were also doors to 'mess' and 'treasury' as well as one unnamed door alongside the one that led up above to the deck in the room you folks are standing in. I may try to start drawing some rudimentary maps of indoors, since people tend to forget the layout once the post with it gets left in the last page.