The germans tried that in the 60s see https://en.wikipedia.org/wiki/Otto_Hahn_(ship) https://en.wikipedia.org/wiki/Otto_Hahn_(ship). It was uneconomical. You

The germans tried that in the 60s see https://en.wikipedia.org/wiki/Otto_Hahn_(ship) https://en.wikipedia.org/wiki/Otto_Hahn_(ship). It was uneconomical. You need specialized engineers for that, you need special permissions for ports and the important canals are off limits due to risk.