Rohloff - I'd change the oil, if the flushing oil comes out milky, flush it again till it doesn't. If you only have one shot of flushing oil, it'd still be better to do it twice with half quantities.
Older hubs were better sealed at the cost of some efficiency, newer ones less so, I preferred the older version. Even with a newer one, it's unlikely a short ride through a ford would allow water to pass the seals, but it's an expensive hub to take chances with.
I have the older version of the SON hub, it survived being in a canal, still in use twenty years later.