So fuel tanks are exempt from pressure/altitude changes?????????
Without vents, a fuel tank would collapse as fuel was sucked out of it. A vented panel would still float if the vent was at the heavy end of the piece. I have not heard it positively stated what material it is made of but it is suggested it would have honeycomb composites, in which case it would not need a lot of trapped air over and above that trapped in the honeycomb, to stay afloat for a long time.
There is nothing extraordinary about this piece appearing as it has. It would be near impossible to pick up on radar and a search aircraft would need to be very close for it to be seen visually.
