Here is an activity that I definitely recommend for visitors.
You board at the dock behind OMSI.
We started worrying about dehydration, so bought some bottled water at OMSI's cafe. The jet boats sell water, and cheaper. We didn't know, but now you do.
One other thing to keep in mind...
This is not a great picture, but in addition to warning about quick stops and things, "You will get wet" and "You may get soaked" -- these are true statements.
It was a warm day and there were many other people enjoying the water. It was the day of the Big Float.
At first you head North up the river, passing under bridges and getting to see some of the working functions of our river, like ships loading grain. Our guide was very informative on Portland industry and history. That kept up as we turned around and headed South.
It gives you a better sense of where things are in relation to each other. We passed Clackamette Park, and places in Lake Oswego, and ended up in Oregon City.
It was interesting learning about the mills on each side, but the best part was seeing the falls. It can be hard to get a good view of them from land.
There were interesting and beautiful things to see all along the way.
Yes, there are times when you are going along really fast, and then do sudden turns (those are the moments you are most likely to get soaked, especially if you are not sitting in the middle of the boat), but there are also times when it is slower and you are being informed.
Six years ago I took a Portland Spirit cruise with some coworkers, and we were captivated by this house, but knew nothing about it. Going back with a guide, now I know that it has never been occupied, though there is a caretaker. Other facts were interesting, but there was a mystery solved too and that was very helpful.
My recommendation of this activity as perfect for visitors is the combination of information at fun.
Jet boat riders will get to see a lot of scenery, they will learn interesting things about the area, and also they will have a lot of fun.
They will get wet.
http://www.willamettejet.com/