We had the same problem on our last visit. The problem is that you can't go directly from FW to CBR (or directly from any resort to another, in most cases). If you can go back to the MK via boat depends on which HDDR show you go to, because at some point the boats stop running.
If you can't go directly back to the MK via boat, you have to take one of the internal FW buses from HDDR to the Outpost, then the quickest way back is to take a bus from there to DTD. From DTD you can get a bus back to CBR.
If you have a car, it might not be a bad idea.