Bosu sign not appearing in Chenyu Vale

Hiya, I've been exploring Chenyu Vale for a little bit now and only just remembered that you can take Bosu's boat from the dock at Qiaoying Village (near the Statue of the Seven) to Yilong Wharf. However, after visiting both docks the sign to summon Bosu just doesn't exist. I would blame my crappy tablet, but to be fair to it, it's actually handled pretty much everything in the game quite well and this seems to specific a glitch. Is there a quest I have to do first? Or am I missing something else? If anyone could point me in the right direction, that would be much appreciated. Thank you!

EDIT: I've completed the regional world quest, and I can now say that I have happily taken my first trip with Bosu! He appears once you've completed it, or if he's not at the harbour, you can summon him like you would the omnibus in Fontaine with the sign that has appeared.