Ship design in the Hellenistic era was advanced by the eastern Successor states. Pontus, on the Black Sea and reliant on sea trade, required a strong navy to protect its interests. Developed from the Greek trireme, ships were improved by adding more banks of rowers. Ships also got bigger, and increased in both length and beam, but at a cost in speed; this allowed larger marine contingents to be carried. Quinqueremes were common from the 4th century BC and featuring rows of five oarsmen, but in the east colossal '20s' and '40s' were constructed. These were usually two hulls in a catamaran arrangement with a fighting platform between them.
