Quote Originally Posted by tom4bren View Post
Not likely that water backed up into your cat unless you turned off the engine whilst it was under water. The exhaust pressure would have kept it from flowing that far up the system. If you turned your engine off, then absolutely it could have.
oops.. I did turn it off while underwater.

However any leak in the exhaust while under water can allow water to back up from the tail pipe because the pressure escapes through the leak. It only takes a small amount of water to shatter a nice hot converter the are porcelain after all and yes they do have platinum in them. Water up the tail pipe is a ricer trick to de cat a car. Couple of things about a clogged/shattered cat if its shattered you should be able to shake it and hear it rattle unless it all fell out. A clogged cat can leave the exhaust smelling like rotten eggs.
Yes maybe I also had a leak, first offroad trip, broke the exhaust system, had it welded back but it might not have been a perfect seal. Yes the mechanic said something about all the porcelain being broken or gone or something like that. Will look for an after market cat, or maybe go decat. Maybe Ill get a couple horsepower.

Thank you guys, will keep you informed.