Whitewater is awesome on a ULI. I have been running rapids all the way up to class V. I haven’t seen anyone else doing it yet. I kayak as well so I paddle my uli with kayakers. I have been honing a technique that makes it possible to run difficult rapids (Class V). I have started running water falls and as of right now I have only worked up to a five foot waterfall. Sticking the landing is difficult but with practice I have been getting it consistently I saw the movie with the rafts on the shoshoe section of CO river and those rapid look like some of the big water rapids I have been doing. If you like river boarding laying down you are going to love the uli standing up.
The ULI is the perfect whitewater board on the market and is extremely durable. Paddling an epoxy board on a river with rocks and current would be a huge waste of money and the fun factor would deminish with all the worrying. Just be careful and start on mellow rapids and work your way up. I have also found great standing waves of rivers that let me have 5 minute surfs with nose rides.