but do not use displacement für the rabbit hole! ;)
But for this you do not need a rabbit hole. It is pretty simple: Earth diameter is about 12750km, the max height difference on earth between mount everest (+9km) and marianna trench (-11km) is 20km. 20km out of 12750km is about 0,16%. Since you can see the water, maraianna trench is out of equasion. The result is 0,07%.