[jackbill]

According to Whorealdo, who claimed to have the Addendum to the autopsy, the baby had a "post-mortem tear". A tear is not a cut, so if he actually had the document, it would seem to limit the possibilities.

I would wonder about a baby's dead body floating around in the bay and being hit by a boat propeller.

[UCANSEE2]

Floating or not, I understand the props come close enough to the bottom to 'pull' up an object, and then slice it , as described.