And, as for small vessels, the highest available movement distance is around 300 kilometers.
Important nobles only used it for moving to people and places in the vicinity. It seems that there also exist cases of shared usage between several noble households in the neighborhood.
Because it isn’t suited for long-distance transport, they arrived at the conclusion that it would be better to travel the sea by boat excluding the inland areas that have no rivers.
Actually, even Margrave Breithilde and his-likes possessed a great number of regular-sized types of ships.