Ship Yoshi did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Ship Yoshi is one of the forms Yoshi can transform into in Yoshi Topsy-Turvy. In this form, Yoshi will float above water, and will continually move forward. By tilting the Game Boy Advance, players are able to change the water level, which is essential to passing through areas requiring Ship Yoshi. If Ship Yoshi touches land and there is no water around him, he cannot move. However, water can touch him and allow him to move again. Getting held back by an obstacle will cause Yoshi to be pushed back. Eventually, this causes him to go off-screen and lose a life.