Fremuff is okay, heard CPM is good. If it's a simple job, kaya rin yan ng Nodalo's, but I'm not sure which Nodalo's branches are good, as some are staffed by apprentices who couldn't weld to save their life (I've had exhausts fall off because of this! ).

I always go to a local shop here in Laguna for mine.

As for water fording, no problem. Unless your idle is precariously low, water in the exhaust won't cause it to die in a flood.