Lecture: At the bottom of the sea. What is under so much water? Synopsis: We know more about the surface of Mars than the bottom of the Earth's oceans or seas.

Two-thirds of the Earth is covered by water, but beneath all that water there is still land, a surface unknown to those who are not scholars and which barely appears in viewers like Google or any of the geolocation applications we have on our mobile phones.

What is under all that blue patch?