I would say you are seeing the bottom of the vest and the person is floating on their back with their shoes and legs bobbing in the water.
If the vest was being worn correctly, yes. But it couldn't have been, because you can't see her head/face. However, Yamamoto IS floating with his face and head showing because his jacket is correctly inflated and fastened. Thus, the leg or legs and shoe you see are more likely to belong to him. Not that it matters whose they are. You've got four potential legs and shoes to play with, before there's a diver. Just IMHO.