He knows how to sail boats. He does not know how to build them. He does, at least, know how to make basic repairs when necessary, to help keep a ship afloat. What he knows the most is the rigging, so he is busy working on that part. He rounded up some rope, and if he needs more, he's had a lot of practice at making rope from vines, and knows right where to find some vines that will work (even if he has to go back to the other side of the village to get them).

He also has a tall, straight, thin tree that he got someone to cut down to use as a mast. He'd have done it himself, but he can't use an ax with only one hand. So far the branches have been removed, and now he's working on stripping the bark off with a tool he found in the boat house. It's not perfect, but it will do, and that's what really matters in a situation like this. Once he has the bark removed and the mast as straight as he can get it, he'll work on rigging the rope to it based on the drawing Moana made, and his own knowledge of how sails and rigging work.

On the beach, with the smell of the ocean nearby, working on a sailing-related task, it's almost like being back in the Enchanted Forest again, with his crew and the knowledge that soon he'll be back on the waves where he belongs. The ache of losing Emma, which he knows will never fully go away, has abated somewhat, and as he scrapes away at the wood, the rhythmic nature of the work has him starting to hum a sea shanty from his sailing days.