Bava Batra 76: The Largest Movable Object That Is Not Alive

How do you acquire a boat? It's a debate between Rav and Shmuel, even after they try to draw the parallel to the acquisition of a large animal and the "pulling" that is effective in that case. In this context, Rabbi Natan raises the discussion of letters - and the Gemara fills in the details about documentation in the transfer of ship ownership. Also, what are the details that are essential for transfer of ownership to take place? Is a document enough? Is a transfer of a document enough? A dispute between Rabbi Yehudah HaNasi and the sages.