River barges transiting a lock - GIF

[carl blum]

Hi Gang:
I remember on the Mississippi River a single tug would be pushing 25 barges at once. If you were in a personal motor boat they would slip you in the lock next to the barges. So a fixed concrete wall on one side and a drifting steel barge on the other, and the top of the lock 38 feet above. Talk about claustrophobic!
Carl.