Back in the mid 1960's, flooded waters covered the rails of the CB&Q in Savannah Ill, if I remember correctly. The Q used their excursion engine, 2-8-2 4960, to pull both freight and passenger trains through the water. They could not use diesels because the water was too deep for the traction motors.
Somewhere there are photos of this, as it was covered in Trains Mag. I think the passenger train might have been the combined TC Zephyr/Empire Bldr/North Coast Ltd.
RAY