Ray's post struck a responsive chord.
I had published a photo of one a few years ago.
I can't recall if it had paddles or not, and I can't find it fast.
Googling on aquatic weed harvesters brings up heaps of material.
Here is just one site:
www.weedharvesters.com. It shows models with paddle wheels, and models without.
I suspect that paddle wheels win in the weed-choked environments because any other propulsion method could become choked.
I demurred from taking Jessie II into Lake Barmah: the water was sufficiently deep, but there were too many weeds. I did strangle the propeller in a side bay where I stopped for lunch above Torumbarry on a recent Murray cruise, but I could recognise the symptoms, and was able to clear the propeller with ease.
Another of the many google-found documents is
www.northcoastweeds.org.au/site-files/docs/forum06/aquatic-weed-mgmt-durre.pdf, showing a paddle-propelled one in use on a Gold Coast (Qld) waterway.
Regards,
Roderick B Smith
Rail News Victoria Editor