Have you ever wondered what was on the otherside of the World. Not just generally but specifically on the other side from where you are in a straight line through the centre of the Earth. That point is called your "antipode" and is the origin of the word "antipodes" when refering to Australia and New Zealand.
There are plenty of maps that allow you to see your antipode displayed graphically, I like the one below. I think it's interesting to note how little overlap there is between the continents. The antipode for most of the land masses is in the ocean. So the answer to the question above is probably "sea".
And if you want a more high tech approach you can use the link below to work it out more accurately