In my setting, all significant powers have rather significant coastline. However, there are no closed seas such as Mediterranean (there are some similar to Caspian sea, but none that would be particularly relevant). So this means that while my "protagonist" state is based on Byzantine Empire, it is rather unlikely that they will have developed anything like Byzantine dromond. When I went to research what ships were used on Atlantic coasts, I found these: Balinger - Wikipedia Birlinn - Wikipedia They appear to be well-suited for what I need. I also know that Britons used sailed warships to combat Caesar's navy - Celts were as technologically advanced as Romans - but these were doomed by the typical vulnerability of sailed ships: Avebury Henge 1 So does anyone know where to find more details? As well as something on oceanic galleys used in Indian ocean, if there were any?