One of the types of boat you see a lot on the Columbia River is the push tug, like the Lewiston of Portland seen on the right. They push barges up and down the river, and they're tall, appearing almost ungainly, so the captain can see over the barge in front of him. It's hard to see from this angle, but you can just make out a tall, straight, dark green bumper at the front of the boat. Push tugs have two of these bumpers, which apparently attach to the barges in various ways. I read something about an electromagnetic attachment, but I don't know if it's used or not. It was shown online as an invention. One thing that surprised me from this angle was the extremely large and long exhaust pipes. I'm sure this tug has a massive engine to push the big barges in the strong river currents. Maybe someone will clue me in on details. It's interesting how many boats and ships we see here in Astoria, Oregon, built and fitted for so many varied and colorful types of work.
I've shown the pilot boat to the left in several posts, and I'm sure you'll see it again. It's such a fixture of the waterfront, and it's extremely active, although its runs are short and it can often be found here in the dock. Not so with the tug, which docks here much less often.