I quickly scanned the Rhine Regulations for Navigation Personnel. The tables starting on page 49 show minimum crew requirements for types of ships and operating modes: https://www.ccr-zkr.org/files/documents/reglementSTF/RPN_010...

It seems to go from a single boatmaster to crews of less than 10. The smallest container ships for inland shipping are about 30-ish containers; the largest about 500.

A truck can do 2 containers with 1 driver.

So, an inland ship can do 15-30 times as many containers per crew, compared to a truck.