Hi Oldsalt
We have two RTM sit on kayaks purchased from Anaconda. They have taken a beating over the past couple of years. Over rocks and causeways, no problems. Good in the surf also. Anaconda has a sale starting today with some kayaks on special. (no affiliation, just happy customer).
Bit of advice. Pay a bit more and get a good paddle. Makes a difference when doing long river trips.
Good luck