I've never understood why people have been saying anything the shape or size of an octaweb could be under that white tarp near the 'X'.
i think its possible that under the tarp one of the legs is still attached to the octoweb
However I'm not sure this is the same piece as being discussed under light tarp.
the part that oshin highlighted are for sure gridfins.
i think there might also be a piece that is a little more than half of a leg sitting out there too.
edit: thinking about it more, its hard to imagine that the octoweb bulkhead would look that good after crushing throught the deck. and perhaps wildly unlikely that it and the interstage bulkhead would look appear in similar condition. perhaps it could have been one or the other but the chances of them being mistaken for each other seems impossible.
LOX umbilical connection/vent?The thing right under your circle is very very clearly a grid fin.