Oxbow, no apology is necessary. There are things that are foreign to all of us. Yes, the concept of inland waterways, (rivers). Mississippi, Columbia, Makenzie, etc. These rivers although big, are not really that wide in comparison to the open ocean, and generally the water is going one way. On the open ocean the ocean currents, wind wave, and swell make it so that pusher tugs, are not used much out here. The whole point being, there is not room for towline, and also the very real action of the barge coming over you in a river. They don't have brakes.
Now a days, (for several years actually) tugs & deep sea ships have bow thrusters, and now stern thrusters these are reversible propellors mounted in the bow & stern for sideways thrusting. On deep sea ships, for ship docking. I'm sure you all have seen harbour tugs, that push deep sea ships into their berth. Well now they have 3000HP thrusters mounted in the ship hulls to help perform this action.
I am attaching here an image, I am rather proud of. There were two ships built in Scotland in 1976. Identical sister ships. The "John Ross", named after a Scottish explorer, and the "Wolraad Woltemade", named for a farmer in South Africa. If you google his name, his story is quite interesting. My uncle Frank, (my mum's brother) was captain on the John Ross. These were the two biggest tugs in the world back then. 19,200 Shaft HP. They were owned by Saftug, (South African Tugboat Company). Home port Cape Town, South Africa. They were deep sea salvage tugs. I recall a time when in my coversations with my uncle, (he had many great stories going right back to WW2). He towed an oil rig from California around Cape Horn to the Congo River, as it was too big to go thru' the Panama Canal. This picture is actually, the Wolraad Woltemade, (now scrapped) the John Ross has been renamed, as the company was sold.