"You want the river to flow rapidly."
Translation:Flumen rapide fluere vis.
I had the same question. In the other forum for this question, there's a good string about the "LATIN INFINITIVE CONSTRUCTION" or something like that. It allowed an infinitive, instead of the subjunctive. I don't know how frequent either construction was; I would have thought subjunctive is much more common since all the Romance languages use subjunctive there.