Those things are badass. First ones i saw were on a kayak fishing float trip. That 8 mile section of the Coosa river stretches from Wetumpka, AL, north to Lake Jordan dam. Twisty, rocky with some Class 2 fall sections.
I saw two thread through a Class 2 spot where I'd turtled over my fishing kayak on a previous float. The boats ate that section like a a potato chip and cruised on.
Was awed and pissed at the same time. Pissed because i love kayaking waters that eat props.