How far an archaic Greek rowing vessel could travel inland

A shallow vessel with roughly fifty rowers could travel far up major European rivers and land on suitable banks, although hauling it between watersheds would be possible rather than easy.

Question

How far up the Po, Rhône, Loire, and Danube could an archaic Greek vessel with about fifty rowers travel, and could its crew portage it between rivers?

Short answer

It could penetrate far inland on suitable rivers and land on flat banks; portage was theoretically possible but would be difficult for the crew.

Notes

The answer assumes a relatively small vessel with at most twenty-five rowers on each side and a shallow draft suitable for inshore water. Its ability to travel inland depends on those hull characteristics. Small Roman river craft provide the comparison for long journeys along the Danube, Rhône, Loire, and Po, although no exact upstream limits are given. Suitable flat banks would allow landing without a developed port. Portage between watersheds is considered theoretically possible, but hauling such a hull overland would be arduous.