A Google Alert directed me to a website that had the following discussion thread:
Q: I accidentally left a 220v transformer outside the house and somehow it flooded outside and left the transformer underwater, Would this thing still work if I let it under the sun for maybe 2-3 days and power it up again? any suggestions?
A: Should be ok, the wire is coated so shouldn't have rusted.
If it wasn't clean rainwater you might want to rinse out any sediment/dirt etc with fresh water and of course leave it to dry before using it.
This is disturbing because it is not correct or safe. The recommendation for transformers is to replace the equipment. More information can be found in the guide Evaluating Water-Damaged Electrical Equipment published by The National Electrical Manufacturers Association (NEMA) – www.nema.org.