I have a ripboard which is made in colorado which is really nice when you want some protection from the rocks. My suggestion is if you want to just surf at play parks a boogie board that you would use on the ocean would be fine but if you plan on running rivers to get a serious river board because you will want the upper body protection. check out the website
it has a lot of good info.
riverboarding is truly whitewater at face level. My best advice is to try and kayak or raft a section of river first before using your river board. Its hard to read the lines and know whats around the corner when your several inches above the water. Also make sure you have a really good pair of Fins.