So i was thinking about the world i set my story in: 

* Set in an age equivalent to the 17th century
* Magic exists, but is not very powerful though very versatile
* Gunpowder was never discovered
* naval control is important, as most of the nations are seperated by oceans

I stumbled over the question if ships would have developed the same (with multiple masts, like Galleons or Viktorian Frigates) or if other forms would have been prefered. I imagined that maybe huge Ballistae could have been used to serve the purpose of sinking enemy ships from a distance.
So, what would you think, how would ships have developed and how would naval battles work when gunpowder was never invented?