whose corpse is discovered?what is shocking about this discovery?

The suspected corpse is Michael. This turns out to be true. Later Mauray's son Bartley is recovered from the sea, just as Mauray had predicted.

Yeah! It was Michael's as the clothes given by the priest of the village to Nora belonged to Michael and it was confirmed that he was dead and got a clean burrial a deep grave on the ground unlike his other brothers who had watery graves deep under the sea.