Rattle on turning engine off

Just turned my engine off and as the engine shuts down there is a rattle from it, thought was a bit odd, so turned the engine on let it run for a few minutes turned it off and rattled again. Ive not heard this rattle before, but prior to the rattle was caught in torrential rain and flooded road maybe half inch deep. Anyone think anything seriously wrong or is it just one of those noises? I have not noticed it before. Cheers Kimbie

Could be the exhaust/cat, if a lot of water went on to the exhaust/cat when hot it may have cracked somthing. The sudden cooling of the exhaust/cat my have made the baffels come loose. Not a problem really Cheers Bob....

Fair dos, will see what its like later when i leave work Cheers Kimbie