My cord is behind the cave straight to the tile and not buried in substrate. The pic doesn't show much and it's too big of file to attach so I didn't post it but under the cave and thin layer of substrate is the tile, under that is the UTH with the cord out the back against the glass in a gap filed in the tile, and under that is another tile. The rock is on the slate off the edge of the hidden UTH and the slate ends by the time you get to the water.