Probably bent con rod or rods, it must've locked up initially before draining the water out via injectors..that'll be just as it stopped running,in the flood. I lived/worked in Worcester area during the bad floods they had a few years ago and had quite a few diesel cars in the garage that'd been in flood water..write offs..

Needs a compression test carrying out, just be warned though that the glo-plugs (where the comp test is usually done from) on these snap off very easily.