If I would have to put it now to be discovered in - lets say- next week - black monolit from Space Odyssey
If i could put it back in time - replika of some ancient piramid with gliphs stating that human flow to Mars to help martians to build the pyramid
BT devices got problems only when water is in between anetna1 and antena2. It does not matter at what altitude the devices are, just what is inbetween them.